Enzymatic Degradation of Proctolin in the CNS of the Locust, Schistocerca Gregaria, by Membrane Bound Enzymes

Abstract

Although a number of mechanisms may be involved in the termination of neuropeptide signals, recent studies in vertebrate neurochemistry have indicated an important role for extracellular membrane enzymes in the inactivation of neuropeptides (Turner et al., 1985). Whether similar membrane enzymes are also involved in the inactivation of insect neuropeptides is unclear. A study on the metabolism of proctolin (Arg-Tyr-Leu-Pro-Thre) by tissues of P. americana showed that this peptide was degraded primarily by two soluble enzyme activities which cleaved the Arg-Tyr and Tyr-Leu bonds (Quistad et al., 1984). Membrane fractions possessed only weak degradative activity towards proctolin.