Polynucleotide phosphorylase

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Image:Crystal structure 1E3P.jpg
Structure of the PNPase trimer
Polynucleotide Phosphorylase
Identifiers
Symbol	PNPASE
Alt. Symbols	PNPase, OLD35, old-35
Entrez	87178
HUGO	23166
OMIM	610316
PDB	1E3P
RefSeq	NM_033109
UniProt	Q8TCS8
Other data
EC number	2.7.7.8
Locus	Chr. 2 p15

Polynucleotide Phosphorylase (PNPase) is bifunctional enzyme with a phosphorolytic 3' to 5' exoribonuclease activity and a 3'-terminal oligonucleotide polymerase activity.^[1] It is involved with mRNA processing and degradation in bacteria, plants,^[1] and in humans.^[1]

In humans, the enzyme is encoded by the PNPT1 gene. In its active form, the protein forms a ring structure consisting of three PNPase molecules. Each PNPase molecule consists of two RNase PH domains, an S1 RNA binding domain and an K-homology domain. The protein is present in eubacteria and in the chloroplasts^[1] and mitochondria^[1] of some eukaryotic cells. In eukaryotes and archaebacteria, a structurally and evolutionary related complex exists, called the exosome ^[1].

Confusingly, the same abbreviation (PNPase), is also used for another, otherwise unrelated, enzyme, namely Purine nucleoside phosphorylase.

References

External links

• MeSH Polynucleotide+Phosphorylase
• Crystal structure of Streptomyces antibioticus PNPase at the RCSB Protein Data Bank

v • d • e Phosphotransferases/kinases (EC 2.7)
2.7.1 - OH acceptor	Hexo- - Gluco- - Fructo- (Hepatic fructo-) - Galacto- - Phosphofructo- (1, 2) - Thymidine - NAD+ - Glycerol - Pantothenate - Mevalonate - Pyruvate - Deoxycytidine - PFP - Diacylglycerol - Bruton's tyrosine - Phosphoinositide 3 (Class I PI 3, Class II PI 3) - Sphingosine
2.7.2 - COOH acceptor	Phosphoglycerate - Aspartate
2.7.3 - N acceptor	Creatine
2.7.4 - PO4 acceptor	Phosphomevalonate - Adenylate - Nucleoside-diphosphate
2.7.6 - P2O7	Ribose-phosphate diphosphokinase - Thiamine pyrophosphokinase
2.7.7 - nucleotidyl-	Integrase - PNPase - Polymerase - RNase PH - UDP-glucose pyrophosphorylase - Galactose-1-phosphate uridylyltransferase -Terminal deoxynucleotidyl transferase - RNA replicase - Reverse transcriptase (Telomerase) - Transposase
2.7.8 - other phos.	N-acetylglucosamine-1-phosphate transferase
2.7.10-11 - protein	Tyrosine - Serine/threonine-specific