Yeast Aldehyde Dehydrogenase

Aldehyde dehydrogenase had previously been purified from autolyzed yeast and had been obtained in crystalline and ultracentrifugally homogeneous form. Further examination of the product by amino-terminal end group analysis revealed gross microheterogeneity which is ascribed to proteolysis. By avoiding autolysis and by using large concentrations of the esterase inhibitors, diisopropyl fluorophosphate and phenylmethylsulfonylfluoride, the enzyme was isolated in a 10-fold greater yield and in a form in which serine was the amino-terminal end group. By proper choice of the inhibitor and its concentration, two proteolytically degraded forms of the enzyme can be isolated in a state of macrohomogeneity. The three enzyme species differ in specific activity but not in their gross kinetic parameters.