KINETIC ASPECTS OF RAT (RATTUS-NORVEGICUS ALBINUS) SUBMANDIBULAR GLANDS LACTIC-DEHYDROGENASE

Submandibular glands of male rats were homogenized with 33 mM sodium p otassium phosphate buffer, pH 6.5, containing 1 mM MgCl2 and 0.1 mM DT T and purified with ammonium sulphate, phosphocellulose chromatography , eluted with KC1 0.5 M, followed by Blue Sepharose CL-6B chromatograp hy, eluted with NADH 0.5 mM. The enzyme kepts stable for 60 days when stored at -15-degrees-C in 33 mM phosphate buffer. In other experiment the enzyme was purified by oxamate-agarose chromatography from a crud e extract of submandibular gland and the results obtained were better than by phosphocellulose and Sepharose CL-6B chromatography. The Km va lues for pyruvate. NADH, lactate and NAD+ were established. Sodium oxa mate at 0.1 and 0.9 mM concentrations inhibited the LDH activity by 40 and 85%, respectively (competitive); with sodium oxalate the inhibiti on was of 30% (uncompetitive) and with 3-acetyl pyridine adenine dinuc leotide was 80%.