[Catalytic properties of alpha-ketoglutarate decarboxylase from bovine brain]

Investigation of the effect of different buffer systems on the rate of alpha-ketoglutarate decarboxylase reaction have shown that the pH optimum is 6.8 in tris-maleic, tris-H3PO4 and KH2PO4-KOH buffers, and it is 7.5 in imidazole buffer. The highest reaction rate was observed when using phosphate containing buffers. The increase of phosphate concentration increased considerably the rate of alpha-ketoglutarate decarboxylase reaction. Mg2+ and Ca2+ were shown to affect slightly the reaction rate. Co2+ and Ag+ slightly inactivated the enzyme. Cu2+ turned to be a very efficient inhibitor of alpha-ketoglutarate decarboxylase reaction. Apparent Mikhaelis constants are determined to be 1.6-10(-3) M for alpha-ketoglutaric acid and 1.7-10(-2)M for 2,6-dichlorphenolindophenol.