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Analysis Note

Protein determined by biuret.

Application

L-Lactic Dehydrogenase from rabbit muscle has been used:for protein-binding measurement to detect the action of oxaloacetate decarboxylase to determine serum L- and D-lactate

Biochem/physiol Actions

Lactic dehydrogenase is responsible for the conversion of pyruvate to lactate in the fermentative metabolism.

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

General description

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: 8.4-8.6Optimal pH : 7.5 .

Physical form

Crystalline suspension in 3.2 M (NH₄)₂SO₄ solution, pH 6.0

Unit Definition

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