Effect of amino acid residues at the cleavable site of substrates on the remarkable activation of thermolysin by salts

Kuniyo Inouye, Soo Bok Lee, Ben'ichiro Tonomura

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The activity of thermolysin in the hydrolysis of N-[3-(2-furyl)acryloyl]-glycyl-L-leucine amide and N-carbobenzoxy-L-aspartyl-L-phenylalanine methyl ester is remarkably enhanced in the presence of high concentrations (1-5 M) of neutral salts. In this study, the effect of salts on such activity has been examined using a series of substrates, furylacryloyl dipeptide amides, which have various hydrophobic amino acids at the cleavable bond. Although the enzyme activity varies widely depending on the substrate employed, the degree of activation at a given concentration of NaCl is considerably similar. This indicates that the degree of activation is not dependent on the hydrophobicity of the amino acid side chains at the scissile bond of the substrates. The molecular activity, k(cat), and Michaelis constant, K(m), were evaluated separately for substrates N-[3-(2-furyl)acryloyl]L-leucyl-L-alanine amide and N-[3-(2-furyl)acryloyl]-L-phenyl-alanyl-L-alanine amide, and the activation was found to be brought about only by an increase in k(cat). The effectiveness of monovalent cations on the increase of k(cat) was determined to follow the order of Na+ > K+ > Li+.

Original languageEnglish
Pages (from-to)133-138
Number of pages6
JournalBiochemical Journal
Issue number1
Publication statusPublished - 1996 Apr 1


All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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