Preparation and kinetic properties of a new form of chymotrypsin which is active at alkaline pH: α1 chymotrypsin

P. Valenzuela, M. L. Bender

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11 Citations (Scopus)

Abstract

The preparation of a new stable and active form of chymotrypsin is described. The enzyme possesses the threonine 147 instead of alanine 149 as the NH2 terminal group of the C chain and has been called α1 chymotrypsin. The conformational transition that affects chymotrypsins at alkaline pH was investigated and compared with that of α- and δ chymotrypsins by studying the kinetic constants and their pH dependencies for the hydrolysis of various specific ester substrates. The k(cat) values obtained with α1 chymotrypsin are similar to those of α- and δ chymotrypsins. The K(m) values showed a progressive increase toward the alkaline pH region. The shape of the K(m) pH profiles closely resemble those of δ chymotrypsin and differ considerably from the behavior of α chymotrypsin. The results strongly implicate the participation of the alanine 149 amino group in the reversible inactivation of α chymotrypsin at high pH.

Original languageEnglish
Pages (from-to)4909-4914
Number of pages6
JournalJournal of Biological Chemistry
Volume248
Issue number14
Publication statusPublished - 1973

ASJC Scopus subject areas

  • Biochemistry
  • Medicine(all)
  • Molecular Biology
  • Cell Biology

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