6-phosphogluconolactonase: Difference between revisions
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{{infobox protein | {{infobox protein | ||
|Name=6-phosphogluconolactonase | |Name=6-phosphogluconolactonase | ||
|caption=Crystallized monomer of 6-phosphogluconolactonase from ''Trypanosoma brucei'' complexed with 6-phosphogluconic acid<ref name="DelarueDuclert-Savatier2007">{{cite journal| | |caption=Crystallized monomer of 6-phosphogluconolactonase from ''Trypanosoma brucei'' complexed with 6-phosphogluconic acid<ref name="DelarueDuclert-Savatier2007">{{cite journal | vauthors = Delarue M, Duclert-Savatier N, Miclet E, Haouz A, Giganti D, Ouazzani J, Lopez P, Nilges M, Stoven V | title = Three dimensional structure and implications for the catalytic mechanism of 6-phosphogluconolactonase from Trypanosoma brucei | journal = Journal of Molecular Biology | volume = 366 | issue = 3 | pages = 868–81 | date = February 2007 | pmid = 17196981 | doi = 10.1016/j.jmb.2006.11.063 }}</ref> | ||
|image=6-phosphogluconolactonase_complexed_with_6-phosphogluconic_acid._PDB-_3E7F.png | |image=6-phosphogluconolactonase_complexed_with_6-phosphogluconic_acid._PDB-_3E7F.png | ||
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'''6-Phosphogluconolactonase (6PGL, PGLS)''' is a cytosolic [[enzyme]] found in all organisms that catalyzes the hydrolysis of [[6-Phosphogluconolactone|6-phosphogluconolactone]] to [[6-Phosphogluconic acid|6-phosphogluconic acid]] in the oxidative phase of the [[pentose phosphate pathway]].<ref name=":2">{{Cite book | '''6-Phosphogluconolactonase (6PGL, PGLS)''' is a cytosolic [[enzyme]] found in all organisms that catalyzes the hydrolysis of [[6-Phosphogluconolactone|6-phosphogluconolactone]] to [[6-Phosphogluconic acid|6-phosphogluconic acid]] in the oxidative phase of the [[pentose phosphate pathway]].<ref name=":2">{{Cite book | title = Biochemistry | edition = Seventh | last = Berg | first = Jeremy | last2 = Tymoczko | first2 = John | last3 = Stryer | first3 = Lubert | name-list-format = vanc | publisher = W.H. Freeman and Company | year = 2012 | isbn = 9781429229364 | location = New York, NY 10010 | pages = 600–601 }}</ref> The tertiary structure of 6PGL employs an [[Alpha/beta hydrolase fold|α/β hydrolase fold]], with active site residues clustered on the loops of the α-helices. Based on the crystal structure of the enzyme, the mechanism is proposed to be dependent on proton transfer by a histidine residue in the active site.<ref name="DelarueDuclert-Savatier2007">{{cite journal | vauthors = Delarue M, Duclert-Savatier N, Miclet E, Haouz A, Giganti D, Ouazzani J, Lopez P, Nilges M, Stoven V | title = Three dimensional structure and implications for the catalytic mechanism of 6-phosphogluconolactonase from Trypanosoma brucei | journal = Journal of Molecular Biology | volume = 366 | issue = 3 | pages = 868–81 | date = February 2007 | pmid = 17196981 | doi = 10.1016/j.jmb.2006.11.063 }}</ref> 6PGL selectively catalyzes the hydrolysis of δ-6-phosphogluconolactone, and has no activity on the [[Lactone#Nomenclature|γ isomer]].<ref name=":3">{{cite journal | vauthors = Miclet E, Stoven V, Michels PA, Opperdoes FR, Lallemand JY, Duffieux F | title = NMR spectroscopic analysis of the first two steps of the pentose-phosphate pathway elucidates the role of 6-phosphogluconolactonase | journal = The Journal of Biological Chemistry | volume = 276 | issue = 37 | pages = 34840–6 | date = September 2001 | pmid = 11457850 | doi = 10.1074/jbc.M105174200 }}</ref> | ||
| title = Biochemistry | |||
| edition = Seventh | |||
| last = Berg | |||
| first = Jeremy | |||
| last2 = Tymoczko | |||
| first2 = John | |||
| last3 = Stryer | |||
| first3 = Lubert | |||
| publisher = W.H. Freeman and Company | |||
| year = 2012 | |||
| isbn = 9781429229364 | |||
| location = New York, NY 10010 | |||
| pages = 600–601 | |||
}}</ref> The tertiary structure of 6PGL employs an [[Alpha/beta hydrolase fold|α/β hydrolase fold]], with active site residues clustered on the loops of the α-helices. Based on the crystal structure of the enzyme, the mechanism is proposed to be dependent on proton transfer by a histidine residue in the active site.<ref name=" | |||
| | |||
| title = Three | |||
| journal = Journal of Molecular Biology | |||
| volume = 366 | |||
| issue = 3 | |||
| pages = | |||
| doi = 10.1016/j.jmb.2006.11.063 | |||
}}</ref> 6PGL selectively catalyzes the hydrolysis of δ-6-phosphogluconolactone, and has no activity on the [[Lactone#Nomenclature|γ isomer]].<ref name=":3">{{ | |||
| | |||
| title = NMR | |||
| journal = Journal of Biological Chemistry | |||
| volume = 276 | |||
| issue = 37 | |||
| pages = | |||
| doi = 10.1074/jbc.M105174200 | |||
}}</ref> | |||
== Enzyme Mechanism == | == Enzyme Mechanism == | ||
6PGL [[hydrolysis]] of [[6-Phosphogluconolactone|6-phosphogluconolactone]] to [[6-Phosphogluconic acid|6-phosphogluconic acid]] has been proposed to proceed via proton transfer to the O5 ring oxygen atom,<ref name=":0" /> similar to [[xylose isomerase]]<ref>{{ | 6PGL [[hydrolysis]] of [[6-Phosphogluconolactone|6-phosphogluconolactone]] to [[6-Phosphogluconic acid|6-phosphogluconic acid]] has been proposed to proceed via proton transfer to the O5 ring oxygen atom,<ref name=":0" /> similar to [[xylose isomerase]]<ref>{{cite journal | vauthors = Whitlow M, Howard AJ, Finzel BC, Poulos TL, Winborne E, Gilliland GL | title = A metal-mediated hydride shift mechanism for xylose isomerase based on the 1.6 A Streptomyces rubiginosus structures with xylitol and D-xylose | journal = Proteins | volume = 9 | issue = 3 | pages = 153–73 | date = 1991-03-01 | pmid = 2006134 | doi = 10.1002/prot.340090302 }}</ref> and [[ribose-5-phosphate isomerase]].<ref>{{cite journal | vauthors = Zhang RG, Andersson CE, Savchenko A, Skarina T, Evdokimova E, Beasley S, Arrowsmith CH, Edwards AM, Joachimiak A, Mowbray SL | title = Structure of Escherichia coli ribose-5-phosphate isomerase: a ubiquitous enzyme of the pentose phosphate pathway and the Calvin cycle | journal = Structure | volume = 11 | issue = 1 | pages = 31–42 | date = January 2003 | pmid = 12517338 | pmc = 2792023 | doi = 10.1016/S0969-2126(02)00933-4 }}</ref> The reaction initiates via attack of a [[hydroxide]] ion at the C5 [[ester]]. A tetrahedral intermediate forms and elimination of the ester linkage follows, aided by donation of a proton from an active site histidine residue. The specific residue that participates in the proton transfer eluded researchers until 2009, as previous structural studies demonstrated two possible conformations of the substrate in the active site, which position the O5 ring oxygen proximal to either an arginine or a histidine residue.<ref name="DelarueDuclert-Savatier2007"/> Molecular dynamic simulations were employed to discover that the residue that donates a proton is histidine, and that the arginine residues are only involved in electric stabilization of the negatively charged phosphate group.<ref name=":0">{{cite journal | vauthors = Duclert-Savatier N, Poggi L, Miclet E, Lopes P, Ouazzani J, Chevalier N, Nilges M, Delarue M, Stoven V | title = Insights into the enzymatic mechanism of 6-phosphogluconolactonase from Trypanosoma brucei using structural data and molecular dynamics simulation | journal = Journal of Molecular Biology | volume = 388 | issue = 5 | pages = 1009–21 | date = May 2009 | pmid = 19345229 | doi = 10.1016/j.jmb.2009.03.063 }}</ref> Electric stabilization of the enzyme-substrate complex also occurs between the product carboxylate and backbone amines of surrounding glycine residues.<ref name=":0" /> | ||
| | |||
| title = A metal-mediated hydride shift mechanism for xylose isomerase based on the 1.6 | |||
| journal = Proteins | |||
| volume = 9 | |||
| issue = 3 | |||
| pages = | |||
| doi = 10.1002/prot.340090302 | |||
}}</ref> and [[ribose-5-phosphate isomerase]].<ref>{{ | |||
| | |||
| title = Structure of Escherichia coli | |||
| journal = Structure | |||
| volume = 11 | |||
| issue = 1 | |||
| pages = 31–42 | |||
| | |||
| pmc = 2792023 | |||
| doi=10.1016/S0969-2126(02)00933-4 | |||
}}</ref> The reaction initiates via attack of a [[hydroxide]] ion at the C5 [[ester]]. A tetrahedral intermediate forms and elimination of the ester linkage follows, aided by donation of a proton from an active site histidine residue. The specific residue that participates in the proton transfer eluded researchers until 2009, as previous structural studies demonstrated two possible conformations of the substrate in the active site, which position the O5 ring oxygen proximal to either an arginine or a histidine residue.<ref name=" | |||
| | |||
| title = Insights | |||
| journal = Journal of Molecular Biology | |||
| volume = 388 | |||
| issue = 5 | |||
| pages = | |||
| doi = 10.1016/j.jmb.2009.03.063 | |||
}}</ref> Electric stabilization of the enzyme-substrate complex also occurs between the product carboxylate and backbone amines of surrounding glycine residues.<ref name=":0" /> | |||
[[File:6PGL_Mechanism.png|none|thumb|711x711px|Proposed mechanism of 6-phosphogluconolactone hydrolysis by 6PGL.]] | [[File:6PGL_Mechanism.png|none|thumb|711x711px|Proposed mechanism of 6-phosphogluconolactone hydrolysis by 6PGL.]] | ||
== Enzyme Structure == | == Enzyme Structure == | ||
6PGL in ''[[Homo sapiens]]'' exists as a monomer at cytosolic physiological conditions, and is composed of 258 amino acid residues with a total molecular mass of ~30 [[Atomic mass unit|kDa]].<ref>{{ | 6PGL in ''[[Homo sapiens]]'' exists as a monomer at cytosolic physiological conditions, and is composed of 258 amino acid residues with a total molecular mass of ~30 [[Atomic mass unit|kDa]].<ref>{{cite journal | vauthors = Collard F, Collet JF, Gerin I, Veiga-da-Cunha M, Van Schaftingen E | title = Identification of the cDNA encoding human 6-phosphogluconolactonase, the enzyme catalyzing the second step of the pentose phosphate pathway(1) | journal = FEBS Letters | volume = 459 | issue = 2 | pages = 223–6 | date = October 1999 | pmid = 10518023 | doi = 10.1016/S0014-5793(99)01247-8 }}</ref> The tertiary structure of the enzyme utilizes an [[Alpha/beta hydrolase fold|α/β hydrolase fold]], with both parallel and anti-parallel [[Beta sheet|β-sheets]] surrounded by eight [[Alpha helix|α-helices]] and five [[310 helix|3<sub>10</sub> helices]].<ref name="DelarueDuclert-Savatier2007"/> Stability of the tertiary structure of the protein is reinforced through salt bridges between [[aspartic acid]] and [[arginine]] residues, and from aromatic side-chain [[Stacking (chemistry)|stacking]] interactions.<ref name="DelarueDuclert-Savatier2007"/> 6PGL isolated from ''[[Trypanosoma brucei]]'' was found to bind with a Zn<sup>+2</sup> ion in a non-catalytic role, but this has not been observed in other organisms, including ''[[Thermotoga maritima]]'' and ''[[Vibrio cholerae]]''.<ref name="DelarueDuclert-Savatier2007"/> | ||
| | |||
| title = Identification of the cDNA encoding human 6-phosphogluconolactonase, the enzyme catalyzing the second step of the pentose phosphate pathway | |||
| journal = FEBS Letters | |||
| volume = 459 | |||
| issue = 2 | |||
| pages = | |||
| doi = 10.1016/S0014-5793(99)01247-8 | |||
}}</ref> The tertiary structure of the enzyme utilizes an [[Alpha/beta hydrolase fold|α/β hydrolase fold]], with both parallel and anti-parallel [[Beta sheet|β-sheets]] surrounded by eight [[Alpha helix|α-helices]] and five [[310 helix|3<sub>10</sub> helices]].<ref name=" | |||
== Biological Function == | == Biological Function == | ||
6-phosphogluconolactonase catalyzes the conversion of 6-phosphogluconolactone to 6-phosphogluconic acid, both intermediates in the oxidative phase of the [[pentose phosphate pathway]], in which [[glucose]] is converted into [[ribulose 5-phosphate]]. The oxidative phase of the pentose phosphate pathway releases CO<sub>2</sub> and results in the generation of two equivalents of [[Nicotinamide adenine dinucleotide phosphate|NADPH]] from NADP<sup>+</sup>. The final product, ribulose 5-phosphate, is further processed by the organism during the non-oxidative phase of the pentose phosphate pathway to synthesize biomolecules including [[nucleotide]]s, [[Adenosine triphosphate|ATP]], and [[Coenzyme A]].<ref name=":2" /> | 6-phosphogluconolactonase catalyzes the conversion of 6-phosphogluconolactone to 6-phosphogluconic acid, both intermediates in the oxidative phase of the [[pentose phosphate pathway]], in which [[glucose]] is converted into [[ribulose 5-phosphate]]. The oxidative phase of the pentose phosphate pathway releases CO<sub>2</sub> and results in the generation of two equivalents of [[Nicotinamide adenine dinucleotide phosphate|NADPH]] from NADP<sup>+</sup>. The final product, ribulose 5-phosphate, is further processed by the organism during the non-oxidative phase of the pentose phosphate pathway to synthesize biomolecules including [[nucleotide]]s, [[Adenosine triphosphate|ATP]], and [[Coenzyme A]].<ref name=":2" /> | ||
The enzyme that precedes 6PGL in the pentose phosphate pathway, [[glucose-6-phosphate dehydrogenase]], exclusively forms the δ-isomer of 6-phosphogluconolactone. However, if accumulated, this compound can undergo intramolecular rearrangement to isomerize to the more stable γ-form, | The enzyme that precedes 6PGL in the pentose phosphate pathway, [[glucose-6-phosphate dehydrogenase]], exclusively forms the δ-isomer of 6-phosphogluconolactone. However, if accumulated, this compound can undergo intramolecular rearrangement to isomerize to the more stable γ-form, which is unable to be hydrolyzed by 6PGL and cannot continue to the non-oxidative phase of the pentose phosphate pathway. By quickly hydrolyzing the δ-isomer of 6-phosphogluconolactone, 6PGL prevents its accumulation and subsequent formation of the γ-isomer, which would be wasteful of the glucose resources available to the cell.<ref name=":3" /> 6-phosphogluconolactone is also susceptible to attack from intracellular [[nucleophile]]s, evidenced by α-N-6-phosphogluconoylation of [[Polyhistidine-tag|His-tagged]] proteins expressed in ''E. coli'',<ref>{{cite journal | vauthors = Geoghegan KF, Dixon HB, Rosner PJ, Hoth LR, Lanzetti AJ, Borzilleri KA, Marr ES, Pezzullo LH, Martin LB, LeMotte PK, McColl AS, Kamath AV, Stroh JG | title = Spontaneous alpha-N-6-phosphogluconoylation of a "His tag" in Escherichia coli: the cause of extra mass of 258 or 178 Da in fusion proteins | journal = Analytical Biochemistry | volume = 267 | issue = 1 | pages = 169–84 | date = February 1999 | pmid = 9918669 | doi = 10.1006/abio.1998.2990 | url = http://www.sciencedirect.com/science/article/pii/S0003269798929906 }}</ref><ref>{{cite journal | vauthors = Kim KM, Yi EC, Baker D, Zhang KY | title = Post-translational modification of the N-terminal His tag interferes with the crystallization of the wild-type and mutant SH3 domains from chicken src tyrosine kinase | journal = Acta Crystallographica Section D | volume = 57 | issue = Pt 5 | pages = 759–62 | date = May 2001 | pmid = 11320329 | doi = 10.1107/s0907444901002918 }}</ref> and efficient hydrolysis of 6-phosphogluconolactone by 6PGL prevents lactone accumulation and consequent toxic reactions from occurring between the lactone intermediate and the cell.<ref name=":3" /> | ||
| | |||
| title = Spontaneous | |||
| journal = Analytical Biochemistry | |||
| volume = 267 | |||
| issue = 1 | |||
| pages = | |||
| doi = 10.1006/abio.1998.2990 | |||
}}</ref><ref>{{ | |||
| | |||
| title = Post-translational modification of the N-terminal His tag interferes with the crystallization of the wild-type and mutant SH3 domains from chicken src tyrosine kinase | |||
| journal = Acta Crystallographica Section D | |||
| volume = 57 | |||
| issue = 5 | |||
| pages = | |||
| doi = 10.1107/s0907444901002918 | |||
}}</ref> and efficient hydrolysis of 6-phosphogluconolactone by 6PGL prevents lactone accumulation and consequent toxic reactions from occurring between the lactone intermediate and the cell.<ref name=":3" /> | |||
== Disease Relevance == | == Disease Relevance == | ||
[[Malaria]]l parasites ''[[Plasmodium berghei]]'' and ''[[Plasmodium falciparum]]'' have been shown to express a bi-functional enzyme that exhibits both [[glucose-6-phosphate dehydrogenase]] and 6-phosphogluconolactonase activity, enabling it to catalyze the first two steps of the pentose phosphate pathway.<ref>{{ | [[Malaria]]l parasites ''[[Plasmodium berghei]]'' and ''[[Plasmodium falciparum]]'' have been shown to express a bi-functional enzyme that exhibits both [[glucose-6-phosphate dehydrogenase]] and 6-phosphogluconolactonase activity, enabling it to catalyze the first two steps of the pentose phosphate pathway.<ref>{{cite journal | vauthors = Clarke JL, Scopes DA, Sodeinde O, Mason PJ | title = Glucose-6-phosphate dehydrogenase-6-phosphogluconolactonase. A novel bifunctional enzyme in malaria parasites | journal = European Journal of Biochemistry | volume = 268 | issue = 7 | pages = 2013–9 | date = April 2001 | pmid = 11277923 | doi = 10.1046/j.1432-1327.2001.02078.x }}</ref> This bifunctional enzyme has been identified as a druggable target for malarial parasites,<ref>{{cite journal | vauthors = Allen SM, Lim EE, Jortzik E, Preuss J, Chua HH, MacRae JI, Rahlfs S, Haeussler K, Downton MT, McConville MJ, Becker K, Ralph SA | title = Plasmodium falciparum glucose-6-phosphate dehydrogenase 6-phosphogluconolactonase is a potential drug target | journal = The FEBS Journal | volume = 282 | issue = 19 | pages = 3808–23 | date = October 2015 | pmid = 26198663 | doi = 10.1111/febs.13380 }}</ref> and [[high-throughput screening]] of small molecule [[Enzyme inhibitor|inhibitors]] has resulted in the discovery of novel compounds that can potentially be translated into potent [[Antimalarial medication|antimalarials]].<ref>{{cite journal | vauthors = Preuss J, Hedrick M, Sergienko E, Pinkerton A, Mangravita-Novo A, Smith L, Marx C, Fischer E, Jortzik E, Rahlfs S, Becker K, Bode L | title = High-throughput screening for small-molecule inhibitors of plasmodium falciparum glucose-6-phosphate dehydrogenase 6-phosphogluconolactonase | journal = Journal of Biomolecular Screening | volume = 17 | issue = 6 | pages = 738–51 | date = July 2012 | pmid = 22496096 | doi = 10.1177/1087057112442382 }}</ref><ref>{{cite journal | vauthors = Preuss J, Maloney P, Peddibhotla S, Hedrick MP, Hershberger P, Gosalia P, Milewski M, Li YL, Sugarman E, Hood B, Suyama E, Nguyen K, Vasile S, Sergienko E, Mangravita-Novo A, Vicchiarelli M, McAnally D, Smith LH, Roth GP, Diwan J, Chung TD, Jortzik E, Rahlfs S, Becker K, Pinkerton AB, Bode L | title = Discovery of a Plasmodium falciparum glucose-6-phosphate dehydrogenase 6-phosphogluconolactonase inhibitor (R,Z)-N-((1-ethylpyrrolidin-2-yl)methyl)-2-(2-fluorobenzylidene)-3-oxo-3,4-dihydro-2H-benzo[b][1,4]thiazine-6-carboxamide (ML276) that reduces parasite growth in vitro | language = EN | journal = Journal of Medicinal Chemistry | volume = 55 | issue = 16 | pages = 7262–72 | date = August 2012 | pmid = 22813531 | pmc = 3530835 | doi = 10.1021/jm300833h }}</ref> | ||
| | |||
| title = Glucose-6-phosphate dehydrogenase-6-phosphogluconolactonase | |||
| journal = European Journal of Biochemistry | |||
| volume = 268 | |||
| issue = 7 | |||
| pages = | |||
| doi = 10.1046/j.1432-1327.2001.02078.x | |||
}}</ref> This bifunctional enzyme has been identified as a druggable target for malarial parasites,<ref>{{ | |||
| | |||
| title = Plasmodium falciparum glucose-6-phosphate dehydrogenase 6-phosphogluconolactonase is a potential drug target | |||
| journal = FEBS Journal | |||
| volume = 282 | |||
| issue = 19 | |||
| pages = | |||
| doi = 10.1111/febs.13380 | |||
}}</ref> and [[high-throughput screening]] of small molecule [[Enzyme inhibitor|inhibitors]] has resulted in the discovery of novel compounds that can potentially be translated into potent [[Antimalarial medication|antimalarials]].<ref>{{ | |||
| | |||
| title = High- | |||
| journal = Journal of Biomolecular Screening | |||
| volume = 17 | |||
| issue = 6 | |||
| pages = | |||
| doi = 10.1177/1087057112442382 | |||
}}</ref><ref>{{ | |||
| | |||
| title = Discovery of a Plasmodium falciparum | |||
| | |||
| journal = Journal of Medicinal Chemistry | |||
| volume = 55 | |||
| issue = 16 | |||
| pages = | |||
| doi = 10.1021/jm300833h | |||
}}</ref> | |||
== References == | == References == | ||
{{Reflist}} | {{Reflist}} | ||
==External links== | == External links == | ||
* {{MeshName|6-phosphogluconolactonase}} | * {{MeshName|6-phosphogluconolactonase}} | ||
* {{cite journal | | * {{cite journal | vauthors = Collard F, Collet JF, Gerin I, Veiga-da-Cunha M, Van Schaftingen E | title = Identification of the cDNA encoding human 6-phosphogluconolactonase, the enzyme catalyzing the second step of the pentose phosphate pathway(1) | journal = FEBS Letters | volume = 459 | issue = 2 | pages = 223–6 | date = October 1999 | pmid = 10518023 | doi = 10.1016/S0014-5793(99)01247-8 }} | ||
{{Pentose phosphate pathway}} | {{Pentose phosphate pathway}} | ||
Latest revision as of 03:31, 7 March 2018
| 6-phosphogluconolactonase | |
|---|---|
| File:6-phosphogluconolactonase complexed with 6-phosphogluconic acid. PDB- 3E7F.png Crystallized monomer of 6-phosphogluconolactonase from Trypanosoma brucei complexed with 6-phosphogluconic acid[1] | |
| Identifiers | |
| Symbol | PGLS |
| Entrez | 25796 |
| HUGO | 8903 |
| OMIM | 604951 |
| RefSeq | NM_012088 |
| UniProt | O95336 |
| Other data | |
| EC number | 3.1.1.31 |
| Locus | Chr. 19 p13.2 |
6-Phosphogluconolactonase (6PGL, PGLS) is a cytosolic enzyme found in all organisms that catalyzes the hydrolysis of 6-phosphogluconolactone to 6-phosphogluconic acid in the oxidative phase of the pentose phosphate pathway.[2] The tertiary structure of 6PGL employs an α/β hydrolase fold, with active site residues clustered on the loops of the α-helices. Based on the crystal structure of the enzyme, the mechanism is proposed to be dependent on proton transfer by a histidine residue in the active site.[1] 6PGL selectively catalyzes the hydrolysis of δ-6-phosphogluconolactone, and has no activity on the γ isomer.[3]
Enzyme Mechanism
6PGL hydrolysis of 6-phosphogluconolactone to 6-phosphogluconic acid has been proposed to proceed via proton transfer to the O5 ring oxygen atom,[4] similar to xylose isomerase[5] and ribose-5-phosphate isomerase.[6] The reaction initiates via attack of a hydroxide ion at the C5 ester. A tetrahedral intermediate forms and elimination of the ester linkage follows, aided by donation of a proton from an active site histidine residue. The specific residue that participates in the proton transfer eluded researchers until 2009, as previous structural studies demonstrated two possible conformations of the substrate in the active site, which position the O5 ring oxygen proximal to either an arginine or a histidine residue.[1] Molecular dynamic simulations were employed to discover that the residue that donates a proton is histidine, and that the arginine residues are only involved in electric stabilization of the negatively charged phosphate group.[4] Electric stabilization of the enzyme-substrate complex also occurs between the product carboxylate and backbone amines of surrounding glycine residues.[4]
Enzyme Structure
6PGL in Homo sapiens exists as a monomer at cytosolic physiological conditions, and is composed of 258 amino acid residues with a total molecular mass of ~30 kDa.[7] The tertiary structure of the enzyme utilizes an α/β hydrolase fold, with both parallel and anti-parallel β-sheets surrounded by eight α-helices and five 310 helices.[1] Stability of the tertiary structure of the protein is reinforced through salt bridges between aspartic acid and arginine residues, and from aromatic side-chain stacking interactions.[1] 6PGL isolated from Trypanosoma brucei was found to bind with a Zn+2 ion in a non-catalytic role, but this has not been observed in other organisms, including Thermotoga maritima and Vibrio cholerae.[1]
Biological Function
6-phosphogluconolactonase catalyzes the conversion of 6-phosphogluconolactone to 6-phosphogluconic acid, both intermediates in the oxidative phase of the pentose phosphate pathway, in which glucose is converted into ribulose 5-phosphate. The oxidative phase of the pentose phosphate pathway releases CO2 and results in the generation of two equivalents of NADPH from NADP+. The final product, ribulose 5-phosphate, is further processed by the organism during the non-oxidative phase of the pentose phosphate pathway to synthesize biomolecules including nucleotides, ATP, and Coenzyme A.[2]
The enzyme that precedes 6PGL in the pentose phosphate pathway, glucose-6-phosphate dehydrogenase, exclusively forms the δ-isomer of 6-phosphogluconolactone. However, if accumulated, this compound can undergo intramolecular rearrangement to isomerize to the more stable γ-form, which is unable to be hydrolyzed by 6PGL and cannot continue to the non-oxidative phase of the pentose phosphate pathway. By quickly hydrolyzing the δ-isomer of 6-phosphogluconolactone, 6PGL prevents its accumulation and subsequent formation of the γ-isomer, which would be wasteful of the glucose resources available to the cell.[3] 6-phosphogluconolactone is also susceptible to attack from intracellular nucleophiles, evidenced by α-N-6-phosphogluconoylation of His-tagged proteins expressed in E. coli,[8][9] and efficient hydrolysis of 6-phosphogluconolactone by 6PGL prevents lactone accumulation and consequent toxic reactions from occurring between the lactone intermediate and the cell.[3]
Disease Relevance
Malarial parasites Plasmodium berghei and Plasmodium falciparum have been shown to express a bi-functional enzyme that exhibits both glucose-6-phosphate dehydrogenase and 6-phosphogluconolactonase activity, enabling it to catalyze the first two steps of the pentose phosphate pathway.[10] This bifunctional enzyme has been identified as a druggable target for malarial parasites,[11] and high-throughput screening of small molecule inhibitors has resulted in the discovery of novel compounds that can potentially be translated into potent antimalarials.[12][13]
References
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Delarue M, Duclert-Savatier N, Miclet E, Haouz A, Giganti D, Ouazzani J, Lopez P, Nilges M, Stoven V (February 2007). "Three dimensional structure and implications for the catalytic mechanism of 6-phosphogluconolactonase from Trypanosoma brucei". Journal of Molecular Biology. 366 (3): 868–81. doi:10.1016/j.jmb.2006.11.063. PMID 17196981.
- ↑ 2.0 2.1 Berg J, Tymoczko J, Stryer L (2012). Biochemistry (Seventh ed.). New York, NY 10010: W.H. Freeman and Company. pp. 600–601. ISBN 9781429229364.
- ↑ 3.0 3.1 3.2 Miclet E, Stoven V, Michels PA, Opperdoes FR, Lallemand JY, Duffieux F (September 2001). "NMR spectroscopic analysis of the first two steps of the pentose-phosphate pathway elucidates the role of 6-phosphogluconolactonase". The Journal of Biological Chemistry. 276 (37): 34840–6. doi:10.1074/jbc.M105174200. PMID 11457850.
- ↑ 4.0 4.1 4.2 Duclert-Savatier N, Poggi L, Miclet E, Lopes P, Ouazzani J, Chevalier N, Nilges M, Delarue M, Stoven V (May 2009). "Insights into the enzymatic mechanism of 6-phosphogluconolactonase from Trypanosoma brucei using structural data and molecular dynamics simulation". Journal of Molecular Biology. 388 (5): 1009–21. doi:10.1016/j.jmb.2009.03.063. PMID 19345229.
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- ↑ Zhang RG, Andersson CE, Savchenko A, Skarina T, Evdokimova E, Beasley S, Arrowsmith CH, Edwards AM, Joachimiak A, Mowbray SL (January 2003). "Structure of Escherichia coli ribose-5-phosphate isomerase: a ubiquitous enzyme of the pentose phosphate pathway and the Calvin cycle". Structure. 11 (1): 31–42. doi:10.1016/S0969-2126(02)00933-4. PMC 2792023. PMID 12517338.
- ↑ Collard F, Collet JF, Gerin I, Veiga-da-Cunha M, Van Schaftingen E (October 1999). "Identification of the cDNA encoding human 6-phosphogluconolactonase, the enzyme catalyzing the second step of the pentose phosphate pathway(1)". FEBS Letters. 459 (2): 223–6. doi:10.1016/S0014-5793(99)01247-8. PMID 10518023.
- ↑ Geoghegan KF, Dixon HB, Rosner PJ, Hoth LR, Lanzetti AJ, Borzilleri KA, Marr ES, Pezzullo LH, Martin LB, LeMotte PK, McColl AS, Kamath AV, Stroh JG (February 1999). "Spontaneous alpha-N-6-phosphogluconoylation of a "His tag" in Escherichia coli: the cause of extra mass of 258 or 178 Da in fusion proteins". Analytical Biochemistry. 267 (1): 169–84. doi:10.1006/abio.1998.2990. PMID 9918669.
- ↑ Kim KM, Yi EC, Baker D, Zhang KY (May 2001). "Post-translational modification of the N-terminal His tag interferes with the crystallization of the wild-type and mutant SH3 domains from chicken src tyrosine kinase". Acta Crystallographica Section D. 57 (Pt 5): 759–62. doi:10.1107/s0907444901002918. PMID 11320329.
- ↑ Clarke JL, Scopes DA, Sodeinde O, Mason PJ (April 2001). "Glucose-6-phosphate dehydrogenase-6-phosphogluconolactonase. A novel bifunctional enzyme in malaria parasites". European Journal of Biochemistry. 268 (7): 2013–9. doi:10.1046/j.1432-1327.2001.02078.x. PMID 11277923.
- ↑ Allen SM, Lim EE, Jortzik E, Preuss J, Chua HH, MacRae JI, Rahlfs S, Haeussler K, Downton MT, McConville MJ, Becker K, Ralph SA (October 2015). "Plasmodium falciparum glucose-6-phosphate dehydrogenase 6-phosphogluconolactonase is a potential drug target". The FEBS Journal. 282 (19): 3808–23. doi:10.1111/febs.13380. PMID 26198663.
- ↑ Preuss J, Hedrick M, Sergienko E, Pinkerton A, Mangravita-Novo A, Smith L, Marx C, Fischer E, Jortzik E, Rahlfs S, Becker K, Bode L (July 2012). "High-throughput screening for small-molecule inhibitors of plasmodium falciparum glucose-6-phosphate dehydrogenase 6-phosphogluconolactonase". Journal of Biomolecular Screening. 17 (6): 738–51. doi:10.1177/1087057112442382. PMID 22496096.
- ↑ Preuss J, Maloney P, Peddibhotla S, Hedrick MP, Hershberger P, Gosalia P, Milewski M, Li YL, Sugarman E, Hood B, Suyama E, Nguyen K, Vasile S, Sergienko E, Mangravita-Novo A, Vicchiarelli M, McAnally D, Smith LH, Roth GP, Diwan J, Chung TD, Jortzik E, Rahlfs S, Becker K, Pinkerton AB, Bode L (August 2012). "Discovery of a Plasmodium falciparum glucose-6-phosphate dehydrogenase 6-phosphogluconolactonase inhibitor (R,Z)-N-((1-ethylpyrrolidin-2-yl)methyl)-2-(2-fluorobenzylidene)-3-oxo-3,4-dihydro-2H-benzo[b][1,4]thiazine-6-carboxamide (ML276) that reduces parasite growth in vitro". Journal of Medicinal Chemistry. 55 (16): 7262–72. doi:10.1021/jm300833h. PMC 3530835. PMID 22813531.
External links
- 6-phosphogluconolactonase at the US National Library of Medicine Medical Subject Headings (MeSH)
- Collard F, Collet JF, Gerin I, Veiga-da-Cunha M, Van Schaftingen E (October 1999). "Identification of the cDNA encoding human 6-phosphogluconolactonase, the enzyme catalyzing the second step of the pentose phosphate pathway(1)". FEBS Letters. 459 (2): 223–6. doi:10.1016/S0014-5793(99)01247-8. PMID 10518023.