Sequence of reactions which follows enzymic oxidation of allylglycine

Abstract

The pathway following flavoprotein-catalyzed oxidation of allylglycine (2-amino-4-pentenoate) was studied and found to depend on the incubation conditions. In N-2-hydroxyethyl-N''-2-ethanesulfonic acid (Hepes) buffer, the oxidation product 2-iminium-4-pentenoate predominantly reacts to form 2-amino-2,4-pentadienoate, a strong noncovalent inhibitor of [hog kidney] D-amino-acid oxidase. However, in pyrophosphate buffer, the more rapid reaction is hydrolysis to form 2-keto-4-pentenoate, which is a substrate for [rabbit muscle] L-lactic dehydrogenase. 2-Keto-4-pentenoate is in rapid equilibrium with 2-hydroxy-2,4-pentadienoate, which is also a strong noncovalent inhibitor of D-amino-acid oxidase. In both systems, these metastable intermediates react in subsequent slower steps to yield trans-2-keto-3-pentenoate, which accumulates in the incubation. Syntheses of trans-2-amino- and trans-2-keto-3-pentenoate are described. Comparisons between the reactivities of acetylenic and olefinic species were made based on the differences between this pathway and that following oxidation of propargylglycine.