Succinic Semialdehyde Dehydrogenase From Human Brain

Succinie semialdehyde dehydrogenase, the enzyme that catalyzes the oxidative step in the γ-aminobutyrate “shunt”, has been purified from human brain and its properties are presented. Noteworthy are the low Michaelis constant, the occurrence of substrate inhibition, the specificity for NAD as the electron acceptor, and the arsenite sensitivity that is potentiated by thiols. Also of interest are the effects of anticonvulsant drugs, steroid hormones, and certain organic compounds upon the activity of the enzyme. A mechanism may be outlined whereby inhibition of succinic semialdehyde oxidation could result in an elevation of brain γ-aminobutyrate and, according to one theory, a consequent elevation of seizure threshold.