L-Lactic Dehydrogenase from rabbit muscle

Research area: Cell Signaling

Lactic Dehydrogenase (LDH) has a total molecular weight of 140 kDa and is composed of 4 subunits which are designated M subunit (muscle) and H subunit (heart). These subunits may be mixed in any of 5 combinations (M4, M3H1, M2H2, MH3, and H4). Skeletal muscle contains LDH that is predominately M4 with some small amounts of M3H and traces of H2H2. The H and M subunits are quite similar in molecular weight, but differ substantially in amino acid composition. Rabbit muscle LDH dissociates into dimeric species (MW = ~70 kDa) in acetate-chloride at pH 5.0, the dissociation is reversible. Biochemistry, 13, 3527-3531 (1974). Oxidizes glyoxylate and lactate.
Isoelectric point: 8.4-8.6
Optimal pH : 7.5 .

L-Lactic Dehydrogenase from rabbit muscle has been used:

• as a component of activation and relaxing solution in ATPase activity and isometric steady-state tension measurements with muscle fiber
• in Trypanosoma congolense pyruvate kinase activity assay
• in pyruvate kinase (PK) assay with rice plastidic PK enzyme OsPK2

Muscle-type Lactic Dehydrogenase (LDH) participates in metabolic pathways and its activity is essential for anaerobic glycolysis. LDH activity is inhibited by ascorbate. LDH regenerates nicotinamide adenine dinucleotide (NAD⁺) from NADH and is industrially useful in poly(lactic acid) production. In the absence of oxygen, LDH participates in a fermentation reaction, catalyzes pyruvate into lactic acid, and oxidizes nicotinamide adenine dinucleotide (NADH) to NAD⁺. Therefore, LDH mediates the production of NAD⁺ essential anaerobic glycolysis pathway. Through this LDH helps maintain the physiological and biochemical functions of the cell in the absence of oxygen.

Also catalyzes the oxidation of other L-2-hydroxymonocarboxylic acids.

Protein determined by biuret.

One unit will reduce 1.0 μmole of pyruvate to L-lactate per min at pH 7.5 at 37 °C.