Inactivation of an NADPH‐dependent succinic semialdehyde reductase by o‐phthalaldehyde

Abstract

Incubation of an NADPH-dependent succiulc semialdehyde reductase from bovine brain with o-phthaluldehyde resulted in a time.dependent loss of enzyme activity. The Inactivation followed pseudo first-order kinetics with the second-order rate constant of 28 M -] s -t. The inactivation was prevented by preincubation of the enzyme with NADPH, but not by sueeinle seminldehyde. There was a linear relationship between Isoindole formation and the loss of enzyme activity. Speetrophotometric studies indicated that complete Inactivation of the enzyme resulted from the formation of one isoindole derivative per molecule of enzyme, which was formed from the reaction of cysteine and lysine residues with o.phthalaldehyde at or near the enzyme active site.

Time Course of Changes in Immunoreactivities of GABA Degradation Enzymes in the Hippocampal CA1 Region after Adrenalectomy in Gerbils

“…They were next incubated with diluted mouse anti-GABA-T [27][28][29], diluted mouse anti-SSADH or anti-SSAR [30,31] overnight at 4°C and subsequently exposed to biotinylated goat anti-mouse IgG and streptavidin peroxidase complex (diluted 1:200, Vector, Burlingame, CA). They were then visualized by staining with 3,3 0 -diaminobenzidine (Sigma, St. Louis, MO) in 0.1 M Tris-HCl buffer (pH 7.2) and mounted on gelatin-coated slides.…”