Merck, L1254-5KU, L-Lactic Dehydrogenase from rabbit muscle

General description
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 .
Application
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

Biochem/physiol Actions
Also catalyzes the oxidation of other L-2-hydroxymonocarboxylic acids.
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.
Analysis Note
Protein determined by biuret.
Other Notes
One unit will reduce 1.0 μmole of pyruvate to L-lactate per min at pH 7.5 at 37 °C.