Kinetics and mechanism of an NADPH-dependent succinic semialdehyde reductase from bovine brain.

An NADPH-dependent succinic semialdehyde reductase has been purified from bovine brain by several chromatographic procedures. The preparation appeared homogeneous on SDS/PAGE. The enzyme is a monomeric protein with a molecular mass of 28 kDa. A number of properties of the bovine brain enzyme, such as substrate specificity, specific activity, molecular mass, optimum pH, amino acid composition, and kinetic parameters, have been determined and compared with those reported for preparations from other sources. The results indicate that the enzyme isolated from bovine brain in the present study is different from those reported for preparations from other sources. The inhibition kinetic patterns obtained when the products of the reaction or substrate analogs are used as inhibitor of the reaction catalyzed by the enzyme are consistent with an ordered sequential mechanism involving the formation of an intermediate ternary complex and in which NADPH is the first substrate to bind the enzyme.