KINETICS OF INACTIVATION OF PENAEUS-PENICILLATUS ACID-PHOSPHATASE DURING INHIBITION BY N-BROMOSUCCINIMIDE

In the present investigation, the inactivation by N-bromosuccinimide o f acid phosphatase from penaeus penicillatus has been studied using th e kinetic method of the substrate reaction during modification of enzy me activity as previously described by Tsou [(1988, Adv. Enzymemol. Re lated Areas Mol. Biol. 61, 381-436]. The results show that inactivatio n of the enzyme by N-bromosuccinimide is a slow, reversible reaction. The results also clearly show that the modification of the tryptophan residues of penaeus penicillatus acid phosphatase by high concentratio ns of N-bromosuccinimide led to the complete inactivation of the enzym e. The microscopic rate constants were determined for the reaction of the inactivator with the free enzyme and with the enzyme-substrate com plex. Comparison of the obtained microscopic rate constants indicates that the presence of the substrate offers marked protection of the enz yme against inactivation by N-bromosuccinimide. The above results sugg est that the tryptophan residue is essential for activity and may be s ituated at the active site of the enzyme.