Lactate dehydrogenase
You don't need to be Editor-In-Chief to add or edit content to WikiDoc. You can begin to add to or edit text on this WikiDoc page by clicking on the edit button at the top of this page. Next enter or edit the information that you would like to appear here. Once you are done editing, scroll down and click the Save page button at the bottom of the page.
| lactate dehydrogenase A
| |
| Identifiers | |
| Symbol | LDHA |
| Entrez | 3939 |
| HUGO | 6535 |
| OMIM | 150000 |
| RefSeq | NM_005566 |
| UniProt | P00338 |
| Other data | |
| EC number | 1.1.1.27 |
| Locus | Chr. 11 p15.4 |
| lactate dehydrogenase B
| |
| Identifiers | |
| Symbol | LDHB |
| Entrez | 3945 |
| HUGO | 6541 |
| OMIM | 150100 |
| RefSeq | NM_002300 |
| UniProt | P07195 |
| Other data | |
| EC number | 1.1.1.27 |
| Locus | Chr. 12 p12.2-12.1 |
| lactate dehydrogenase C
| |
| Identifiers | |
| Symbol | LDHC |
| Entrez | 3948 |
| HUGO | 6544 |
| OMIM | 150150 |
| RefSeq | NM_002301 |
| UniProt | P07864 |
| Other data | |
| EC number | 1.1.1.27 |
| Locus | Chr. 11 p15.5-15.3 |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Phone:617-525-6884
Please Join in Editing This Page and Apply to be an Editor-In-Chief for this topic: There can be one or more than one Editor-In-Chief. You may also apply to be an Associate Editor-In-Chief of one of the subtopics below. Please mail us [2] to indicate your interest in serving either as an Editor-In-Chief of the entire topic or as an Associate Editor-In-Chief for a subtopic. Please be sure to attach your CV and or biographical sketch.
Lactate dehydrogenase (LDH) is an enzyme (EC 1.1.1.27) present in a wide variety of organisms, including plants and animals.
Reactions
It catalyses the interconversion of pyruvate and lactate with concomitant interconversion of NADH and NAD+. At high concentrations of lactate, the enzyme exhibits feedback inhibition and the rate of conversion of pyruvate to lactate is decreased.
It also catalyzes the dehydrogenation of 2-Hydroxybutyrate, but it is a much poorer substrate than lactate. There is little to no activity with beta-hydroxybutyrate.
Enzyme isoforms
- LDH-1 (4H) - in the heart
- LDH-2 (3H1M) - in the reticuloendothelial system
- LDH-3 (2H2M) - in the lungs
- LDH-4 (1H3M) - in the kidneys
- LDH-5 (4M) - in the liver and striated muscle
The five isozymes that are usually described in the literature each contain four subunits. The major isozymes of skeletal muscle and liver, M4, has four muscle (M) subunits; while H (heart)4 is the main isozymes for heart muscle in most species, containing 4 H subunits. The other variants contain both types of subunits.
Usually LDH-2 is the predominant form in the serum. A LDH-1 level higher than the LDH-2 level (a "flipped pattern"), suggests myocardial infarction (damage to heart tissues releases heart LDH, which is rich in LDH-1, into the bloodstream). The use of this phenomenon to diagnose infarction has been largely superseded by the use of Troponin I or T measurement.
Genetics in Humans
The M and H subunits are encoded by two different genes:
- The M subunit is encoded by LDHA, located on chromosome 11p15.4 (Online 'Mendelian Inheritance in Man' (OMIM) 150000)
- The H subunit is encoded by LDHB, located on chromosome 12p12.2-p12.1 (Online 'Mendelian Inheritance in Man' (OMIM) 150100)
- A third isoform, LDHC or LDHX, is expressed only in the testis (Online 'Mendelian Inheritance in Man' (OMIM) 150150); its gene is likely a duplicate of LDHA and is also located on the eleventh chromosome (11p15.5-p15.3)
Mutations of the M subunit have been linked to the rare disease exertional myoglobinuria (see OMIM article), and mutations of the H subunit have been described but do not appear to lead to disease.
Medical use
Hemolysis
In medicine, LDH is often used as a marker of tissue breakdown as LDH is abundant in red blood cells and can function as a marker for hemolysis. A blood sample that has been handled incorrectly can show false-positively high levels of LDH due to erythrocyte damage.
It can also be used as a marker of myocardial infarction. Following a myocardial infarction, levels of LDH peak at 3-4 days and remain elevated for up to 10 days. In this way, elevated levels of LDH can be useful for determining if a patient has had a myocardial infarction if they come to doctors several days after an episode of chest pain.
Tissue turnover
Other uses are assessment of tissue breakdown in general; this is possible when there are no other indicators of hemolysis. It is used to follow-up cancer (especially lymphoma) patients, as cancer cells have a high rate of turnover with destroyed cells leading to an elevated LDH activity.
Exudates and transudates
Measuring LDH in fluid aspirated from a pleural effusion (or pericardial effusion) can help in the distinction between exudates (actively secreted fluid, e.g. due to inflammation) or transudates (passively secreted fluid, due to a high hydrostatic pressure or a low oncotic pressure). LDH is elevated (>200 U/l) in an exudate and low in a transudate. In empyema, the LDH levels generally will exceed 1000 U/l.
Meningitis and encephalitis
The enzyme is also found in cerebrospinal fluid where high levels of lactate dehydrogenase in cerebrospinal fluid are often associated with bacterial meningitis. High levels of the enzyme can also be found in cases of viral meningitis, generally indicating the presence of encephalitis and poor prognosis.
HIV and elevated LDH
LDH is often measured in HIV patients as a non-specific marker for Pneumocystis jiroveci (formerly Pneumocystis carinii) pneumonia (PCP). Elevated LDH in the setting of upper respiratory symptoms in an HIV patient suggests, but is not diagnostic for, PCP.
Complete Differential Diagnosis of an Elevated Lactate Dehydrogenase (LDH)
- Acute tubular necrosis
- Cardiac arrhythmia
- Cirrhosis
- Congestive Heart Failure
- Dermatomyositis
- Erythrocyte destruction from prosthetic heart valve
- Glomerulonephritis
- Hemolytic anemia
- Hepatic failure
- Hepatitis
- Hepatoma
- Infarction
- Infectious mononucleosis
- Ischemic colitis
- Kidney transplant rejection
- Leukemia
- Liver abscess
- Lymphoma
- Megaloblastic anemia
- Multiple Myeloma
- Muscular trauma
- Myocardial Infarction
- Myocarditis
- Myopathy
- Neuroblastoma
- Neurogenic muscular atrophy
- Pancreatitis
- Pneumonia
- Portal hypertension
- Postoperative
- Progressive muscular dystrophy
- Pulmonary embolism
- Testicular cancer
See also
References
- IUBMB entry for 1.1.1.27
- BRENDA references for 1.1.1.27 (Recommended.)
- PubMed references for 1.1.1.27
- PubMed Central references for 1.1.1.27
- Google Scholar references for 1.1.1.27
External links
Oxidoreductases: alcohol oxidoreductases (EC 1.1) | |
|---|---|
| 1.1.1 NAD/NADP acceptor | Carbohydrate dehydrogenases - Alcohol dehydrogenase - Glycerol-3-phosphate dehydrogenase - L-xylulose reductase - Aldose reductase - Lactate dehydrogenase - 3-Hydroxyacyl CoA dehydrogenase - Malate dehydrogenase - Isocitrate dehydrogenase - Phosphogluconate dehydrogenase - Glucose-6-phosphate dehydrogenase - HMG-CoA reductase - Β-Ketoacyl ACP reductase - Hydroxysteroid dehydrogenase: 11 Beta (HSD11B1, HSD11B2) - 3 Beta (3-beta-HSD) - 17 Beta - Carnitine dehydrogenase - Beta-hydroxybutyryl-CoA dehydrogenase - IMP dehydrogenase - DXP reductoisomerase |
| 1.1.3 oxygen acceptor | Glucose oxidase - L-gulonolactone oxidase - Xanthine oxidase |
Carbohydrate metabolism: glycolysis/gluconeogenesis enzymes | |
|---|---|
| Glycolysis | Glucokinase/Hexokinase/Glucose 6-phosphatase - Glucose isomerase - Phosphofructokinase 1/Fructose 1,6-bisphosphatase - Aldolase - Triosephosphate isomerase - Glyceraldehyde 3-phosphate dehydrogenase - Phosphoglycerate kinase - Phosphoglycerate mutase - Enolase - Pyruvate kinase |
| Gluconeogenesis only | Pyruvate carboxylase - Phosphoenolpyruvate carboxykinase - from lactate (Cori cycle): Lactate dehydrogenase - from alanine (Alanine cycle): Alanine transaminase |
| Regulatory | Phosphofructokinase 2/Fructose 2,6-bisphosphatase - Bisphosphoglycerate mutase |
it:L-lattato deidrogenasi nl:Melkzuurdehydrogenase ja:乳酸脱水素酵素fi:Laktaattidehydrogenaasi
Acknowledgement and Attribution Regarding Sources of Content
Some of the initial content on this page may be incorporated in part from copyleft sources in the public domain including wikis such as Wikipedia and AskDrWiki. Drug information for patients came from the The National Library of Medicine. Infectious disease information may have come from the Centers for Disease Control (CDC). Differential Diagnoses are drawn from clinicians as well as an amalgamation of 3 sources: 1.The Disease Database; 2. Kahan, Scott, Smith, Ellen G. In A Page: Signs and Symptoms. Malden, Massachusetts: Blackwell Publishing, 2004:3; 3. Sailer, Christian, Wasner, Susanne. Differential Diagnosis Pocket. Hermosa Beach, CA: Borm Bruckmeir Publishing LLC, 2002:7 .
