Purification and characterization of protease III from Escherichia coli

J Biol Chem. 1979 Jun 10;254(11):4698-706.

Abstract

An endoproteolytic enzyme of Escherichia coli, designated protease III, has been purified about 9,600-fold to homogeneity with a 6% yield. The purified enzyme consists of a single polypeptide chain of Mr 110,000 and is most active at pH 7.4. Protease III is very sensitive to metal-chelating agents and reducing agents. The EDTA-inactivated enzyme can be reactivated by Zn2+, Co2+ or Mn2+. Protease III is devoid of activity toward aminopeptidase, carboxypeptidase, or esterase substrates but rapidly degrades small proteins. When fragments of beta-galactosidase are used as substrates for protease III, the enzyme preferentially degrades proteins with molecular weights of less than 7,000. Protease III cleaves the oxidized insulin B chain at two sites with an initial rapid cleavage at Tyr-Leu (16-17) and a second slower cut at Phe-Tyr (25-26).

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Cations, Divalent
  • Drug Stability
  • Endopeptidases / isolation & purification
  • Endopeptidases / metabolism*
  • Escherichia coli / enzymology*
  • Kinetics
  • Metalloendopeptidases
  • Molecular Weight
  • Substrate Specificity

Substances

  • Cations, Divalent
  • Endopeptidases
  • Metalloendopeptidases
  • auR protein, Staphylococcus aureus