title: Kinetics of chymotrypsin- and papain-catalysed synthesis of [leucine]enkephalin and [methionine]enkephalin.
abstract: The proteinase-catalysed synthesis of [Leu]enkephalin and [Met]enkephalin was studied kinetically. N alpha-t-Butoxycarbonyl-amino acids and peptides or their ethyl esters served as acyl donors, and amino acid phenylhydrazides were used as acyl acceptors. Initial-velocity measurements of alpha-chymotrypsin-catalysed peptide synthesis gave rise to kinetic patterns that are compatible with a ping-pong mechanism modified by a hydrolytic branch. Initial-rate and alternative-substrate inhibition patterns for papain-controlled peptide-bond formation are consistent with a sequential ordered mechanism with the acyl donor as the obligatory first substrate. On the basis of the observed kinetic features, reaction mechanisms are proposed for chymotrypsin- and papain-catalysed peptide synthesis that inversely equal those describing the pathways of proteolysis. The respective initial-velocity expressions for bireactant systems are given, along with the numerical values of the corresponding kinetic parameters.
mesh_terms: D002384:Catalysis; D002851:Chromatography, High Pressure Liquid; D002918:Chymotrypsin / Q000378:metabolism*; D004743:Enkephalin, Leucine / Q000096:biosynthesis*; D004744:Enkephalin, Methionine / Q000096:biosynthesis*; D007700:Kinetics; D008956:Models, Chemical; D009842:Oligopeptides / Q000378:metabolism; D010206:Papain / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D009842:Oligopeptides; D004744:Enkephalin, Methionine; D004743:Enkephalin, Leucine; D002918:Chymotrypsin; D010206:Papain