Kinetic study on the reaction mechanism of pantothenase: existence of an acyl-enzyme intermediate and role of general acid catalysis

Biochemistry. 1978 Nov 14;17(23):4932-8. doi: 10.1021/bi00616a012.

Abstract

A kinetic study was performed on the reaction mechanism of pantothenase (EC 3.5.1.22) catalyzed hydrolysis of the pantothenic acid. A nonlinear progress curve is derived if the reaction occurs at low buffer concentrations. The nonlinearity is due to partial reversibility of the reaction; an acylenzyme (pantoyl-enzyme) is formed during the reaction, and beta-alanine, the other end product, is able to react with the acyl-enzyme and return back to pantothenate. The dependence of the beta-alanine return reaction on buffer concentration and on pH suggests a general acid catalysis during the reaction. A reaction mechanism is suggested, in which the -NH3+ form of beta-alanine participates in the return reaction, and the deacylation of the acyl-enzyme is acid catalyzed.

MeSH terms

  • Acylation
  • Alanine / pharmacology
  • Amidohydrolases / metabolism*
  • Kinetics
  • Mathematics
  • Pantothenic Acid
  • Protein Binding
  • Pseudomonas fluorescens / enzymology

Substances

  • Pantothenic Acid
  • Amidohydrolases
  • pantothenase
  • Alanine