Malate dehydrogenase: Definition from Answers.com

Malate dehydrogenase

Structure of the protein with attached sugars

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Malate dehydrogenase (EC 1.1.1.37) is an enzyme in the citric acid cycle that catalyzes the conversion of malate into oxaloacetate (using NAD⁺) and vice versa (this is a reversible reaction). Malate dehydrogenase is not to be confused with malic enzyme, which catalyzes the conversion of malate to pyruvate producing NADPH.

Malate dehydrogenase is also involved in gluconeogenesis, the synthesis of glucose from smaller molecules. Pyruvate in the mitochondria is acted upon by pyruvate carboxylase to form oxaloacetate, a citric acid cycle intermediate. In order to get the oxaloacetate out of the mitochondria, malate dehydrogenase reduces it to malate, and it then traverses the inner mitochondrial membrane. Once in the cytosol, the malate is oxidized back to oxaloacetate by cytosolic malate dehydrogenase. Finally, phosphoenol-pyruvate carboxy kinase (PEPCK) converts oxaloacetate to phosphoenol pyruvate.

Isozymes

Humans and most other mammals express the following two malate dehydrogenases:

malate dehydrogenase 1, NAD (soluble)
Identifiers
Symbol	MDH1
Entrez	4190
HUGO	6970
OMIM	154200
RefSeq	NM_005917
UniProt	P40925
Other data
EC number	1.1.1.37
Locus	Chr. 2 p23

malate dehydrogenase 2, NAD (mitochondrial)
Identifiers
Symbol	MDH2
Entrez	4191
HUGO	6971
OMIM	154100
RefSeq	NM_005918
UniProt	P40926
Other data
EC number	1.1.1.37
Locus	Chr. 7 cen-q22

References

Banaszak, LJ, Bradshaw RA (1975). "Malate dehydrogenase". in Boyer PD. The Enzymes. 11 (3rd ed.). New York: Academic Press. pp. 369–396.
Guha A, Englard S, Listowsky I (February 1968). "Beef heart malic dehydrogenases. VII. Reactivity of sulfhydryl groups and conformation of the supernatant enzyme". J. Biol. Chem. 243 (3): 609–15. PMID 5637713.
McReynolds MS, Kitto GB (February 1970). "Purification and properties of Drosophila malate dehydrogenases". Biochim. Biophys. Acta 198 (2): 165–75. PMID 4313528.
Wolfe RG, Nielands JB (July 1956). "Some molecular and kinetic properties of heart malic dehydrogenase". J. Biol. Chem. 221 (1): 61–9. PMID 13345798.

External links

MeSH Malate+dehydrogenase

v • d • e Oxidoreductases: alcohol oxidoreductases (EC 1.1)

1.1.1: NAD/NADP acceptor	Alcohol dehydrogenase · Aldo-keto reductase (1A1, 1B1, 1B10, 1C1, 1C3, 1C4, 7A2) · Aldose reductase · Carbohydrate dehydrogenases · Carnitine dehydrogenase · DXP reductoisomerase · Glucose-6-phosphate dehydrogenase · Glycerol-3-phosphate dehydrogenase · HMG-CoA reductase · 3-Hydroxyacyl CoA dehydrogenase · Beta-hydroxybutyryl-CoA dehydrogenase · Isocitrate dehydrogenase · IMP dehydrogenase · Β-Ketoacyl ACP reductase · Lactate dehydrogenase · Malate dehydrogenase · Phosphogluconate dehydrogenase · L-threonine dehydrogenase · L-xylulose reductase · Sorbitol dehydrogenase Hydroxysteroid dehydrogenase: 3 Beta (3-beta-HSD, NSDHL) · 11 Beta (HSD11B1, HSD11B2) · 17 Beta

1.1.2: cytochrome acceptor	D-lactate dehydrogenase (cytochrome) · D-lactate dehydrogenase (cytochrome c-553) · Mannitol dehydrogenase (cytochrome)

1.1.3: oxygen acceptor	Glucose oxidase · L-gulonolactone oxidase · Xanthine oxidase

1.1.4: disulfide as acceptor	Vitamin K epoxide reductase · Vitamin-K-epoxide reductase (warfarin-insensitive)

1.1.5: quinone/similar acceptor	Quinoprotein glucose dehydrogenase

1.1.99: other acceptors	Choline dehydrogenase · L2HGDH

Metabolism: Citric acid cycle enzymes

Cycle

Citrate synthase · Aconitase · Isocitrate dehydrogenase · Oxoglutarate dehydrogenase · Succinyl CoA synthetase
Succinate dehydrogenase (SDHA) · Fumarase · Malate dehydrogenase

Anaplerotic

to acetyl-CoA	Pyruvate dehydrogenase complex (E1, E2, E3) (regulated by Pyruvate dehydrogenase kinase and Pyruvate dehydrogenase phosphatase)

to α-ketoglutaric acid	Glutamate dehydrogenase

to succinyl-CoA	Methylmalonyl-CoA mutase

to oxaloacetate	Pyruvate carboxylase · Aspartate transaminase

see also intermediates

v • d • e Mitochondrial enzymes and transporters

Outer membrane	fatty acid degradation (Carnitine palmitoyltransferase I, Long fatty acyl CoA synthetase) tryptophan metabolism (Kynureninase) monoamine neurotransmitter metabolism (Monoamine oxidase)

Intermembrane space	Adenylate kinase - Creatine kinase

Inner membrane	oxidative phosphorylation (Coenzyme Q - cytochrome c reductase, Cytochrome c, NADH dehydrogenase, Succinate dehydrogenase) pyrimidine metabolism (Dihydroorotate dehydrogenase) mitochondrial shuttle (Malate-aspartate shuttle, Glycerol phosphate shuttle) other (Glutamate aspartate transporter, Glycerol-3-phosphate dehydrogenase, ATP synthase, Carnitine palmitoyltransferase II, Uncoupling protein)

Matrix	citric acid cycle (Citrate synthase, Aconitase, Isocitrate dehydrogenase, Oxoglutarate dehydrogenase, Succinyl coenzyme A synthetase, Fumarase, Malate dehydrogenase) anaplerotic reactions (Aspartate transaminase, Glutamate dehydrogenase, Pyruvate dehydrogenase complex) urea cycle (Carbamoyl phosphate synthetase I, Ornithine transcarbamylase, N-Acetylglutamate synthase) alcohol metabolism (ALDH2)

Other/to be sorted	steroidogenesis (Cholesterol side-chain cleavage enzyme, Steroid 11-beta-hydroxylase, Aldosterone synthase)

Mitochondrial DNA	Complex I (MT-ND1, MT-ND2, MT-ND3, MT-ND4, MT-ND4L, MT-ND5, MT-ND6) - Complex III (MT-CYB) - Complex IV (MT-CO1, MT-CO2, MT-CO3) ATP synthase (MT-ATP6, MT-ATP8) tRNA (MT-TA, MT-TC, MT-TD, MT-TE, MT-TF, MT-TG, MT-TH, MT-TI, MT-TK, MT-TL1, MT-TL2, MT-TM, MT-TN, MT-TP, MT-TQ, MT-TR, MT-TS1, MT-TS2, MT-TT, MT-TV, MT-TW, MT-TY)

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