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Title: Excess zinc ions are a competitive inhibitor for carboxypeptidase A

Abstract

The mechanism for inhibition of enzyme activity by excess zinc ions has been studied by kinetic and equilibrium dialysis methods at pH 8.2, I = 0.5 M. With carboxypeptidase A (bovine pancreas), peptide (carbobenzoxyglycyl-L-phenylalanine and hippuryl-L-phenylalanine) and ester (hippuryl-L-phenyl lactate) substrates were inhibited competitively by excess zinc ions. The K/sub i/ values for excess zinc ions with carboxypeptidase A at pH 8.2 are all similar. The apparent constant for dissociation of excess zinc ions from carboxypeptidase A was also obtained by equilibrium dialysis at pH 8.2 and was 2.4 x 10/sup -5/ M, very close to the K/sub i/ values above. With arsanilazotyrosine-248 carboxypeptidase A ((Azo-CPD)Zn)), hippuryl-L-phenylalanine, carbobenzoxyglycyl-L-phenylalanine, and hippuryl-L-phenyl lactate were also inhibited with a competitive pattern by excess zinc ions, and the K/sub i/ values were (3.0-3.5) x 10/sup -5/ M. The apparent constant for dissociation of excess zinc ions from arsanilazotyrosine-248 carboxypeptidase A, which was obtained from absorption changes at 510 nm, was 3.2 x 10/sup -5/ M and is similar to the K/sub i/ values for ((Azo-CPD)Zn). The apparent dissociation and inhibition constants, which were obtained by inhibition of enzyme activity and spectrophotometric and equilibrium dialysis methods with native carboxypeptidase A and arsanilazotyrosine-248 carboxypeptidase A, weremore » almost the same. This agreement between the apparent dissociation and inhibition constants indicates that the zinc binding to the enzymes directly relates to the inhibition of enzyme activity by excess zinc ions. Excess zinc ions were competitive inhibitors for both peptide and ester substrates. This behavior is believed to arise by the excess zinc ions fixing the enzyme in a conformation to which the substrates cannot bind.« less

Authors:
; ;
Publication Date:
Research Org.:
Nagoya City Univ., Japan
OSTI Identifier:
5402043
Resource Type:
Journal Article
Journal Name:
Biochemistry; (United States)
Additional Journal Information:
Journal Volume: 26:20
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; CARBOXYPEPTIDASES; BIOCHEMICAL REACTION KINETICS; ZINC COMPOUNDS; BIOLOGICAL EFFECTS; CATIONS; CATTLE; DOSE-RESPONSE RELATIONSHIPS; ENZYME ACTIVITY; ENZYME INHIBITORS; PANCREAS; ANIMALS; BODY; CHARGED PARTICLES; DIGESTIVE SYSTEM; DOMESTIC ANIMALS; ENDOCRINE GLANDS; ENZYMES; GLANDS; HYDROLASES; IONS; KINETICS; MAMMALS; ORGANS; PEPTIDE HYDROLASES; REACTION KINETICS; RUMINANTS; VERTEBRATES; 550300* - Cytology; 550200 - Biochemistry

Citation Formats

Hirose, J., Ando, S., and Kidani, Y. Excess zinc ions are a competitive inhibitor for carboxypeptidase A. United States: N. p., 1987. Web. doi:10.1021/bi00394a041.
Hirose, J., Ando, S., & Kidani, Y. Excess zinc ions are a competitive inhibitor for carboxypeptidase A. United States. doi:10.1021/bi00394a041.
Hirose, J., Ando, S., and Kidani, Y. Tue . "Excess zinc ions are a competitive inhibitor for carboxypeptidase A". United States. doi:10.1021/bi00394a041.
@article{osti_5402043,
title = {Excess zinc ions are a competitive inhibitor for carboxypeptidase A},
author = {Hirose, J. and Ando, S. and Kidani, Y.},
abstractNote = {The mechanism for inhibition of enzyme activity by excess zinc ions has been studied by kinetic and equilibrium dialysis methods at pH 8.2, I = 0.5 M. With carboxypeptidase A (bovine pancreas), peptide (carbobenzoxyglycyl-L-phenylalanine and hippuryl-L-phenylalanine) and ester (hippuryl-L-phenyl lactate) substrates were inhibited competitively by excess zinc ions. The K/sub i/ values for excess zinc ions with carboxypeptidase A at pH 8.2 are all similar. The apparent constant for dissociation of excess zinc ions from carboxypeptidase A was also obtained by equilibrium dialysis at pH 8.2 and was 2.4 x 10/sup -5/ M, very close to the K/sub i/ values above. With arsanilazotyrosine-248 carboxypeptidase A ((Azo-CPD)Zn)), hippuryl-L-phenylalanine, carbobenzoxyglycyl-L-phenylalanine, and hippuryl-L-phenyl lactate were also inhibited with a competitive pattern by excess zinc ions, and the K/sub i/ values were (3.0-3.5) x 10/sup -5/ M. The apparent constant for dissociation of excess zinc ions from arsanilazotyrosine-248 carboxypeptidase A, which was obtained from absorption changes at 510 nm, was 3.2 x 10/sup -5/ M and is similar to the K/sub i/ values for ((Azo-CPD)Zn). The apparent dissociation and inhibition constants, which were obtained by inhibition of enzyme activity and spectrophotometric and equilibrium dialysis methods with native carboxypeptidase A and arsanilazotyrosine-248 carboxypeptidase A, were almost the same. This agreement between the apparent dissociation and inhibition constants indicates that the zinc binding to the enzymes directly relates to the inhibition of enzyme activity by excess zinc ions. Excess zinc ions were competitive inhibitors for both peptide and ester substrates. This behavior is believed to arise by the excess zinc ions fixing the enzyme in a conformation to which the substrates cannot bind.},
doi = {10.1021/bi00394a041},
journal = {Biochemistry; (United States)},
number = ,
volume = 26:20,
place = {United States},
year = {1987},
month = {10}
}