Partial purification and properties of Cunninghamella elegans L-alanine dehydrogenase

L-Alanine dehydrogenase was partially purified from the mycelial extracts of Cunninghamella elegans. The purified enzyme was fractionated by TEAE-cellulose column chromatography into two fractions (subunits) designated as fractions I and II. The activity of both fractions in the aminating reaction is 8 times higher than the activity of the deaminating reaction. pH-Optimal for reductive amination of pyruvate by both fractions were 8 and 10 for oxidative deamination of L-alanine. The Km values of fractions I and II for L-alanine, NAD+, pyruvate, NH4+ and NADH were estimated. Both fractions of L-alanine dehydrogenase were absolutely specific for L-alanine in the oxidative deamination reaction. Maximal activity of both fractions occurred at 40 degrees C. Inhibition by iodoacetate and activation by SH-compounds suggest that sulfhydryl groups may participate in enzyme activity. The 2 fractions were activated with Co2+, Fe2+, Ca2+, Mg2+ and Mn2+ ions, while Zn2+ inhibited both fractions. Stability of the enzyme under different conditions was investigated.