Studies of the Activity of Chymotrypsin

  • Hess G
  • McConn J
  • Ku E
 et al. 
  • 9

    Readers

    Mendeley users who have this article in their library.
  • 101

    Citations

    Citations of this article.

Abstract

Physical and chemical studies of chymotrypsin in solution and kinetic measurements of individual steps in reactions catalysed by this hydrolytic enzyme are reported. The solution studies also provide a basis for correlation of individual reaction steps with structural information obtained by Drs Blow and Hartley and discussed at this Discussion. The rate and equilibrium constants pertaining to the three-step mechanism shown below have been determined for the chymotrypsin catalysed hydrolysis of three specific ester substrates-the ethyl esters of N-acetyl-L-tyrosine, N-acetyl-L-tryptophan, and N-acetyl-L-phenylalanine-at selected pH values with use of both flow and relaxation techniques.$E + S \overset{K'_S}{\rightleftharpoons} ES
earrow\rightarrow^{P_1}_{k_{23}} EP_2 \rightarrow_{k_{23}} E + P_2$ where E is enzyme, S is substrate, ES is a complex, EP$_2$ is an intermediate compound, and the products P$_1$ and P$_2$ are, respectively, an alcohol or amine and an acid. The hydrolysis of chymotrypsin specific substrates is shown to be considerably more complex than is indicated by this previously proposed mechanism. In addition to the steps shown, there exist a number of ionization and conformational equilibria which account for the bell-shaped pH-rate profiles observed for chymotrypsin catalysed reactions. A catalytically active enzyme conformation, which is in pH dependent equilibrium with a catalytically inactive conformation, is shown to have its origin in the enzyme activation mechanism. In the chymotrypsin catalysed hydrolysis of an amide substrate, furylacryloyltrypto-phanamide, there has been detected an additional intermediate which differs from the intermediate EP$_2$ observed in ester hydrolysis.

Get free article suggestions today

Mendeley saves you time finding and organizing research

Sign up here
Already have an account ?Sign in

Find this document

Get full text

Authors

  • G P Hess

  • J McConn

  • E Ku

  • G McConkey

Cite this document

Choose a citation style from the tabs below

Save time finding and organizing research with Mendeley

Sign up for free