Human cystatin C. role of the N-terminal segment in the inhibition of human cysteine proteinases and in its inactivation by leucocyte elastase

Biochem J. 1991 Feb 1;273 ( Pt 3)(Pt 3):621-6. doi: 10.1042/bj2730621.

Abstract

Leucocyte elastase in catalytic amounts was observed to rapidly cleave the Val-10-Gly-11 bond of the human cysteine-proteinase inhibitor cystatin C at neutral pH. The resulting modified inhibitor had size and amino acid composition consistent with a cystatin C molecule devoid of the N-terminal Ser-1-Val-10 decapeptide. Leucocyte-elastase-modified cystatin C had more than 240-fold lower affinity than native cystatin C for papain. Removal of the N-terminal decapeptide of human cystatin C also decreased inhibition of human cathepsins B and L by three orders of magnitude, but decreased inhibition of cathepsin H by only 5-fold. A tripeptidyldiazomethane analogue of of the N-terminal portion of cystatin C was a good inhibitor of cathepsins B and L but a poor inhibitor of cathepsin H. It therefore appears that amino acid side chains of the N-terminal segment of cystatin C bind in the substrate-binding pockets of cathepsins B and L but not in those of cathepsin H. It is argued that the N-terminal cystatin C interaction with cathepsin B is physiologically important and hence that leucocyte elastase could have a function as a regulator of extracellular cysteine-proteinase inhibitory activity at sites of inflammation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Cystatin C
  • Cystatins / genetics
  • Cystatins / isolation & purification
  • Cystatins / metabolism*
  • Electrophoresis, Agar Gel
  • Electrophoresis, Polyacrylamide Gel
  • Escherichia coli / genetics
  • Humans
  • Kinetics
  • Leukocyte Elastase
  • Molecular Sequence Data
  • Molecular Weight
  • Pancreatic Elastase / metabolism*
  • Recombinant Proteins / isolation & purification
  • Recombinant Proteins / metabolism
  • Substrate Specificity

Substances

  • CST3 protein, human
  • Cystatin C
  • Cystatins
  • Recombinant Proteins
  • Pancreatic Elastase
  • Leukocyte Elastase