Mar 11, 1976

Kinetic properties of pulmonary angiotensin-converting enzyme. Hydrolysis of hippurylglycylglycine

Biochimica Et Biophysica Acta
F E DorerL T Skeggs

Abstract

Some of the kinetic properties of angiotensin-converting enzyme (peptidyl-dipeptide hydrolase, EC 3.4.15.1) purified from hog lung have been determined using hippurylglycylglycine as substrate. The effects of pH and ionic environment on enzyme activity are complex and interdependent. At 0.1 M NaCl, the pH-activity curve shows an abrupt decrease in V/Km as the pH rises from 6 to 6.5, implying that ionization of a group in the enzyme with a pK in this range aids in binding of the substrate. Chloride is required for enzyme activity; there are two phases in the effect of NaCl. At both pH 6 AND 8, THE FIRST PHASE (UP TO 0.1 M NaCl) is activation. The second phase (above 0.1 M) at pH 6 is inhibition, while at pH 8 there is further activation which appears to be dependent upon ionic strength rather than a specific Cl-effect. Activation by cobalt and inhibition by EDTA are somewhat more effective at pH 6 than at pH 8. The nonapeptide inhibitor less than Glu-Trp-Pro-Arg-Pro-Gln-Ile-Pro-Pro is nearly equipotent at both pH 6 and 8, but Arg-Pro-Pro is more inhibitory at pH 8 than at pH 6.

  • References10
  • Citations31

References

  • References10
  • Citations31

Mentioned in this Paper

Lung
Oligopeptides
Prolylarginine
Enzyme Activity
Blood Enzyme Activity (Lab Test)
Lung Diseases
Metabolic Inhibition
Sodium Chloride
Sodium Chloride, (24)NaCl
Chloride Measurement

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