lactic dehydrogenase

乳酸脱水素酵素 乳酸デヒドロゲナーゼ lactate dehydrogenase LDH

WordNet

1. of or relating to or obtained from milk (especially sour milk or whey); "lactic acid"; "lactic fermentation"

PrepTutorEJDIC

1. 乳の;乳から採れる

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/10/15 02:44:02」(JST)

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Lactate dehydrogenase
Identifiers
EC number	1.1.1.27
CAS number	9001-60-9
Databases
IntEnz	IntEnz view
BRENDA	BRENDA entry
ExPASy	NiceZyme view
KEGG	KEGG entry
MetaCyc	metabolic pathway
PRIAM	profile
PDB structures	RCSB PDB PDBe PDBsum
Gene Ontology	AmiGO / EGO
Search PMC articles PubMed articles NCBI proteins

A lactate dehydrogenase (LDH or LD) is an enzyme found in nearly all living cells (animals, plants, and prokaryotes). LDH catalyzes the conversion of pyruvate to lactate and back, as it converts NADH to NAD⁺ and back. A dehydrogenase is an enzyme that transfers a hydride from one molecule to another.

LDH exist in four distinct enzyme classes. This article is about the common NAD(P)-dependent L-lactate dehydrogenase. Other LDHs act on D-lactate and/or are dependent on cytochrome c: D-lactate dehydrogenase (cytochrome)) and L-lactate (L-lactate dehydrogenase (cytochrome)).

LDH has been of medical significance because it is found extensively in body tissues, such as blood cells and heart muscle. Because it is released during tissue damage, it is a marker of common injuries and disease such as heart failure.

Reactions

Lactate dehydrogenase catalyzes the interconversion of pyruvate and lactate with concomitant interconversion of NADH and NAD⁺. It converts pyruvate, the final product of glycolysis, to lactate when oxygen is absent or in short supply, and it performs the reverse reaction during the Cori cycle in the liver. 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.

Reaction catalyzed by lactate dehydrogenase

Arrow pushing mechanism for the reaction catalyzed by lactate dehydrogenase

Isozymes in mammals

Lactate dehydrogenase is composed of four subunits (tetramer). The two most common subunits are the LDH-M and LDH-H protein, encoded by the LDHA and LDHB genes, respectively. These two subunits can form five possible tetramers (isoenzymes): 4H, 4M, and the three mixed tetramers (3H1M, 2H2M, 1H3M). These five isoforms are enzymatically similar but show different tissue distribution: The major isoenzymes of skeletal muscle and liver, M₄, has four muscle (M) subunits, while H₄ is the main isoenzymes for heart muscle in most species, containing four heart (H) subunits.

• LDH-1 (4H)—in the heart and in RBC (red blood cells), as well as the brain.
• LDH-2 (3H1M)—in the reticuloendothelial system
• LDH-3 (2H2M)—in the lungs
• LDH-4 (1H3M)—in the kidneys, placenta, and pancreas
• LDH-5 (4M)—in the liver and striated muscle

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.

There are two more mammalian LDH subunits that can be included in LDH tetramers: LDHC and LDHBx. LDHC is a testes-specific LDH protein, that is encoded by the LDHC gene. LDHBx is a peroxisome-specific LDH protein. LDHBx is the readthrough-form of LDHB. LDHBx is generated by translation of the LDHB mRNA, but the stop codon is interpreted as an amino acid-encoding codon. In consequence, translation continues to the next stop codon. This leads to the addition of seven amino acid acids to the normal LDH-H protein. The extension contains a peroxisomal targeting signal, so that LDHBx is imported into the peroxisome.

lactate dehydrogenase A (subunit M)
Human lactate dehydrogenase M4 (the isoenzyme found in skeletal muscle). From PDB: 1I10​.
Identifiers
Symbol	LDHA
Alt. symbols	LDHM
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 (subunit H)
Crystal structure of B-lactate dehydrogenase From PDB: 1T2F​.
Identifiers
Symbol	LDHB
Alt. symbols	LDHL
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
Crystal structure of C-lactate dehydrogenase From PDB: 2LDX​.
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

Protein families

D-lactate dehydrogenase, membrane binding
crystal structure of d-lactate dehydrogenase, a peripheral membrane respiratory enzyme.
Identifiers
Symbol	Lact-deh-memb
Pfam	PF09330
Pfam clan	CL0277
InterPro	IPR015409
SCOP	1f0x
SUPERFAMILY	1f0x
Available protein structures: Pfam structures PDB RCSB PDB; PDBe; PDBj PDBsum structure summary

lactate/malate dehydrogenase, NAD binding domain
Identifiers
Symbol	Ldh_1_N
Pfam	PF00056
Pfam clan	CL0063
InterPro	IPR001236
SCOP	6ldh
SUPERFAMILY	6ldh
Available protein structures: Pfam structures PDB RCSB PDB; PDBe; PDBj PDBsum structure summary

lactate/malate dehydrogenase, alpha/beta C-terminal domain
Identifiers
Symbol	Ldh_1_C
Pfam	PF02866
Pfam clan	CL0341
InterPro	IPR022383
PROSITE	PDOC00066
SCOP	6ldh
SUPERFAMILY	6ldh
Available protein structures: Pfam structures PDB RCSB PDB; PDBe; PDBj PDBsum structure summary

The family also contains L-lactate dehydrogenases that catalyse the conversion of L-lactate to pyruvate, the last step in anaerobic glycolysis. Malate dehydrogenases that catalyse the interconversion of malate to oxaloacetate and participate in the citric acid cycle, and L-2-hydroxyisocaproate dehydrogenases are also members of the family. The N-terminus is a Rossmann NAD-binding fold and the C-terminus is an unusual alpha+beta fold.

Interactive pathway map

Click on genes, proteins and metabolites below to link to respective articles.

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|{{{bSize}}}px|alt=Glycolysis and Gluconeogenesis edit]]

File:WP534.png

Glycolysis and Gluconeogenesis edit

Enzyme regulation

This protein may use the morpheein model of allosteric regulation.

Ethanol-induced hypoglycemia

Ethanol is dehydrogenated to acetaldehyde by alcohol dehydrogenase, and further into acetic acid by acetaldehyde dehydrogenase. During this reaction 2 NADH are produced. If large amounts of ethanol are present, then large amounts of NADH are produced, leading to a depletion of NAD⁺. Thus, the conversion of pyruvate to lactate is increased due to the associated regeneration of NAD⁺. Therefore, anion-gap metabolic acidosis (lactic acidosis) may ensue in ethanol poisoning.

The increased NADH/NAD+ ratio also can cause hypoglycemia in an (otherwise) fasting individual who has been drinking and is dependent on gluconeogenesis to maintain blood glucose levels. Alanine and lactate are major gluconeogenic precursors that enter gluconeogenesis as pyruvate. The high NADH/NAD+ ratio shifts the lactate dehydrogenase equilibrium to lactate, so that less pyruvate can be formed and, therefore, gluconeogenesis is impaired.

Substrate regulation

LDH is also regulated by the relative concentrations of its substrates. LDH becomes more active under periods of extreme muscular output due to an increase in substrates for the LDH reaction. When skeletal muscles are pushed to produce high levels of power, the demand for ATP in regards to aerobic ATP supply leads to an accumulation of free ADP, AMP, and Pi. The subsequent glycolytic flux, specifically production of NADH and pyruvate, exceeds the capacity for pyruvate dehydrogenase and other shuttle enzymes to metabolize pyruvate. The flux through LDH increases in response to increased levels of pyruvate and NADH to metabolize pyruvate into lactate.

Transcriptional regulation

LDH undergoes transcriptional regulation by PGC-1α. PGC-1α regulates LDH by decreasing LDH A mRNA transcription and the enzymatic activity of pyruvate to lactate conversion.

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)

• The fourth isoform is localized in the peroxisome. It is tetramer containing one LDHBx subunit, which is also encoded by LDHB gene. The LDHBx protein is seven amino acids longer than the LDHB (LDH-H) protein. This amino acid extension is generated by functional translational readthrough.

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.

Role in muscular fatigue

The onset of acidosis during periods of intense exercise is commonly been attributed to accumulation of lactic acid. From this reasoning, the idea of lactate production being a primary cause of muscle fatigue during exercise has been widely adopted. A closer, mechanistic analysis of lactate production under anaerobic conditions shows that there is no biochemical evidence for the production of lactate through LDH contributing to acidosis. While LDH activity is correlated to muscle fatigue, the production of lactate by means of the LDH complex works as a system to delay the onset of muscle fatigue.

LDH works to prevent muscular failure and fatigue in multiple ways. The lactate-forming reaction generates cytosolic NAD+, which feeds into the glyceraldehyde 3-phosphate dehydrogenase reaction to help maintain cytosolic redox potential and promote substrate flux through the second phase of glycolysis to promote ATP generation. This, in effect, provides more energy to contracting muscles under heavy workloads. The production and removal of lactate from the cell also ejects a proton consumed in the LDH reaction- the removal of excess protons produced in the wake of this fermentation reaction serves to act as a buffer system for muscle acidosis. Once proton accumulation exceeds the rate of uptake in lactate production and removal through the LDH symport, muscular acidosis occurs.

Medical relevance

LDH is a protein that normally appears throughout the body in small amounts. Many cancers can raise LDH levels, so LDH may be used as a tumor marker, but at the same time, it is not useful in identifying a specific kind of cancer. Measuring LDH levels can be helpful in monitoring treatment for cancer. Noncancerous conditions that can raise LDH levels include heart failure, hypothyroidism, anemia, pre-eclampsia, meningitis, encephalitis, acute pancreatitis, HIV and lung or liver disease.

Tissue breakdown releases LDH, and therefore LDH can be measured as a surrogate for tissue breakdown, e.g. hemolysis. LDH is measured by the lactate dehydrogenase (LDH) test (also known as the LDH test or Lactic acid dehydrogenase test). Comparison of the measured LDH values with the normal range help guide diagnosis.

Cancer cells

LDH is involved in tumor initiation and metabolism. Cancer cells rely on anaerobic respiration for the conversion of glucose to lactate even under oxygen-sufficient conditions (a process known as the Warburg effect). This state of fermentative glycolysis is catalyzed by the A form of LDH. This mechanism allows tumorous cells to convert the majority of their glucose stores into lactate regardless of oxygen availability, shifting use of glucose metabolites from simple energy production to the promotion of accelerated cell growth and replication. For this reason, LDH A and the possibility of inhibiting its activity has been identified as a promising target in cancer treatments focused on preventing carcinogenic cells from proliferating.

Comparison of LDH activity in normal and cancerous cell metabolisms

Chemical inhibition of LDH A has demonstrated marked changes in metabolic processes and overall survival carcinoma cells. Oxamate is a cytosolic inhibitor of LDH A that significantly decreases ATP production in tumorous cells as well as increasing production of reactive oxygen species (ROS). These ROS drive cancer cell proliferation by activating kinases that drive cell cycle progression growth factors at low concentrations, but can damage DNA through oxidative stress at higher concentrations. Secondary lipid oxidation products can also inactivate LDH and impact its ability to regenerate NADH, directly disrupting the enzymes ability to convert lactate to pyruvate.

While recent studies have shown that LDH activity is not necessarily an indicator of metastatic risk, LDH expression can act as a general marker in the prognosis of cancers. Expression of LDH5 and VEGF in tumors and the stroma has been found to be a strong prognostic factor for diffuse or mixed-type gastric cancers.

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 (where the level of LDH1 is higher than that of LDH2, ie the LDH Flip, as normally, in serum, LDH2 is higher than LDH1) can be useful for determining whether 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). The usual criterion is that a ratio of fluid LDH versus upper limit of normal serum LDH of more than 0.6 or ²⁄₃ indicates an exudate, while a ratio of less indicates a transudate. Different laboratories have different values for the upper limit of serum LDH, but examples include 200 and 300 IU/L. In empyema, the LDH levels, in general, will exceed 1000 IU/L.

Meningitis and encephalitis

High levels of lactate dehydrogenase in cerebrospinal fluid are often associated with bacterial meningitis. In the case of viral meningitis, high LDH, in general, indicates the presence of encephalitis and poor prognosis.

HIV

LDH is often measured in HIV patients as a non-specific marker for pneumonia due to Pneumocystis jiroveci (PCP). Elevated LDH in the setting of upper respiratory symptoms in an HIV patient suggests, but is not diagnostic for, PCP. However, in HIV-positive patients with respiratory symptoms, a very high LDH level (>600 IU/L) indicated histoplasmosis (9.33 more likely) in a study of 120 PCP and 30 histoplasmosis patients.

Dysgerminoma

Elevated LDH is often the first clinical sign of a rare malignant cell tumor called a dysgerminoma. Not all dysgerminomas produce LDH, and this is often a non-specific finding.

Prokaryotes

A cap-membrane-binding domain is found in prokaryotic lactate dehydrogenase. This consists of a large seven-stranded antiparallel beta-sheet flanked on both sides by alpha-helices. It allows for membrane association.

See also

• Dehydrogenase
• Oxidoreductase
• Lactate

References

Further reading

• Johnson WT, Canfield WK (1985). "Intestinal absorption and excretion of zinc in streptozotocin-diabetic rats as affected by dietary zinc and protein.". J Nutr 115 (9): 1217–27. PMID 3897486. 
• Ein SH, Mancer K, Adeyemi SD (1985). "Malignant sacrococcygeal teratoma--endodermal sinus, yolk sac tumor--in infants and children: a 32-year review.". J Pediatr Surg 20 (5): 473–7. doi:10.1016/s0022-3468(85)80468-1. PMID 3903096. 
• Azuma M, Shi M, Danenberg KD, Gardner H, Barrett C, Jacques CJ, Sherod A, Iqbal S, El-Khoueiry A, Yang D, Zhang W, Danenberg PV, Lenz HJ (2007). "Serum lactate dehydrogenase levels and glycolysis significantly correlate with tumor VEGFA and VEGFR expression in metastatic CRC patients.". Pharmacogenomics 8 (12): 1705–13. doi:10.2217/14622416.8.12.1705. PMID 18086000. 
• Masepohl B, Klipp W, Pühler A (1988). "Genetic characterization and sequence analysis of the duplicated nifA/nifB gene region of Rhodobacter capsulatus.". Mol Gen Genet 212 (1): 27–37. doi:10.1007/bf00322441. PMID 2836706. 
• Galardo MN, Regueira M, Riera MF, Pellizzari EH, Cigorraga SB, Meroni SB (2014). "Lactate Regulates Rat Male Germ Cell Function through Reactive Oxygen Species.". PLoS ONE 9 (1): e88024. doi:10.1371/journal.pone.0088024. PMC 3909278. PMID 24498241. 
• Tesch P, Sjödin B, Thorstensson A, Karlsson J (1978). "Muscle fatigue and its relation to lactate accumulation and LDH activity in man.". Acta Physiol Scand 103 (4): 413–20. doi:10.1111/j.1748-1716.1978.tb06235.x. PMID 716962. 
• Beck O, Jernström B, Martinez M, Repke DB (1988). "In vitro study of the aromatic hydroxylation of 1-methyltetrahydro-beta-carboline (methtryptoline) in rat.". Chem Biol Interact 65 (1): 97–106. doi:10.1016/0009-2797(88)90034-8. PMID 3345575. 
• Summermatter S, Santos G, Pérez-Schindler J, Handschin C (2013). "Skeletal muscle PGC-1α controls whole-body lactate homeostasis through estrogen-related receptor α-dependent activation of LDH B and repression of LDH A.". Proc Natl Acad Sci U S A 110 (21): 8738–43. doi:10.1073/pnas.1212976110. PMC 3666691. PMID 23650363. 
• Robergs RA, Ghiasvand F, Parker D (2004). "Biochemistry of exercise-induced metabolic acidosis.". Am J Physiol Regul Integr Comp Physiol 287 (3): R502–16. doi:10.1152/ajpregu.00114.2004. PMID 15308499. 
• Kresge N, Simoni RD, Hill RL (2005). "Otto Fritz Meyerhof and the elucidation of the glycolytic pathway.". J Biol Chem 280 (4): e3. PMID 15665335. 

This article incorporates text from the public domain Pfam and InterPro IPR015409

UpToDate Contents

全文を閲覧するには購読必要です。 To read the full text you will need to subscribe.

• 1. 乳酸アシドーシスの原因 causes of lactic acidosis
• 2. 乳酸脱水素酵素欠損症 lactate dehydrogenase deficiency
• 3. 肝酵素および肝機能検査値の異常が認められた患者に対するアプローチ approach to the patient with abnormal liver biochemical and function tests
• 4. ミトコンドリアミオパシー：治療 mitochondrial myopathies treatment
• 5. ミトコンドリアミオパシー：臨床的特徴および診断 mitochondrial myopathies clinical features and diagnosis

English Journal

• Mendeliome sequencing enables differential diagnosis and treatment of neonatal lactic acidosis.

• Fazeli W1, Karakaya M2, Herkenrath P1, Vierzig A1, Dötsch J1, von Kleist-Retzow JC1, Cirak S3,4,5.
• Molecular and cellular pediatrics.Mol Cell Pediatr.2016 Dec;3(1):22. doi: 10.1186/s40348-016-0050-x. Epub 2016 Jun 17.
• BACKGROUND: Neonatal lactic acidosis can be associated to severe inborn errors of metabolism. Rapid identification of the underlying disorder may improve the clinical management through reliable counseling of the parents and adaptation of the treatment.METHODS: We present the case of a term newborn
• PMID 27317552

• Diammonium phosphate stimulates transcription of L-lactate dehydrogenase leading to increased L-lactate production in the thermotolerant Bacillus coagulans strain.

• Sun L1,2, Li Y1,3, Wang L1, Wang Y2, Yu B4.
• Applied microbiology and biotechnology.Appl Microbiol Biotechnol.2016 Aug;100(15):6653-60. doi: 10.1007/s00253-016-7379-x. Epub 2016 Feb 17.
• Exploration of cost-effective fermentation substrates for efficient lactate production is an important economic objective. Although some organic nitrogen sources are also cheaper, inorganic nitrogen salts for lactate fermentation have additional advantages in facilitating downstream procedures and s
• PMID 26883345

• Prenatal presentation of pyruvate dehydrogenase complex deficiency.

• Natarajan N1, Tully HM1, Chapman T2.
• Pediatric radiology.Pediatr Radiol.2016 Aug;46(9):1354-7. doi: 10.1007/s00247-016-3585-z. Epub 2016 Mar 30.
• We present the case of a female infant referred for prenatal MR evaluation of ventriculomegaly, which had been attributed by the referring obstetrician to aqueductal stenosis. Fetal MR confirmed ventriculomegaly but also demonstrated cerebral volume loss and white matter abnormalities. After birth,
• PMID 27026023

Japanese Journal

• Stimulation of D- and L-lactate dehydrogenases transcriptional levels in presence of diammonium hydrogen phosphate resulting to enhanced lactic acid production by Lactobacillus strain

• Journal of bioscience and bioengineering 124(6), 674-679, 2017-12
• NAID 40021420122

• Anchorless cell surface proteins function as laminin-binding adhesins in Lactobacillus rhamnosus FSMM22

• Fems Microbiology Letters 364(6), fnx056, 2017-03
• NAID 120006414712

• Pulmonary Intravascular Large B-cell Lymphoma (IVLBCL) Disguised as an Asthma Exacerbation in a Patient with Asthma

• Internal Medicine 56(14), 1885-1891, 2017
• NAID 130005773843

Related Links

• Lactate dehydrogenase test: MedlinePlus Medical Encyclopedia

Lactate dehydrogenase (LDH) is a protein that helps produce energy in the body. An LDH test measures the amount of LDH in the blood. ... When the needle is inserted to draw blood, some people feel moderate pain. Others feel ...

• LD: The Test | Lactate Dehydrogenase; LD Test: Lactate ...

Explaines how the lactate dehydrogenase (LD) test is used, when an LD test is ordered, and what the results of an LD test might mean. An LD blood test may be used: as a general indicator of the existence and severity ...

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関連記事	「lactic」「dehydrogenase」「dehydrogenases」

「lactic」

　　[★]

• adj.

• 乳酸の

関

lactate、lactic acid

　 　

「dehydrogenase」

　　[★] 脱水素酵素 デヒドロゲナーゼ

「dehydrogenases」

　　[★] 脱水素酵素 デヒドロゲナーゼ