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On the size of the active site in proteases II. Carboxypeptidase-A
- Source :
- Biochemical and Biophysical Research Communications. 29:862-867
- Publication Year :
- 1967
- Publisher :
- Elsevier BV, 1967.
-
Abstract
- The size of the active site of carboxypeptidase-A was investigated by studying the kinetics of hydrolysis of peptides of L-alanine, D-alanine and L-phenylalanine, as well as of a number of their N-benzyloxycarbonyl, N-acetyl, N-phenylproprionyl and N-methyloxycarbonyl derivatives. From a comparison of the various kinetic parameters ( K m, kcat) it was concluded that the active site of this enzyme extends over about 18 A. The binding area can be divided into 5 “subsites”, each accommodating one amino acid residue (or blocking group) of the substrate. By comparing K m values of pairs of substrates containing either a methyl or a benzyl side-chain in equivalent positions, it was shown that the binding area as a whole has a larger affinity towards the aromatic residues. Substitution of a D-residue for an L-residue reduced kcat values rather than K m. In addition a remarkable affinity for the urethane-grouping located specifically at subsite S3 was found. A methyloxycarbonyl or benzyloxy — carbonyl group occupying this subsite caused a 5-fold increase in K m as compared with an acetyl or phenylproprionyl group, respectively. Methyloxycarbonyl or benzyloxycarbonyl groups in subsites S2 or S4 showed no such effect.
- Subjects :
- Electrophoresis
Paper
Chemical Phenomena
Stereochemistry
Kinetics
Biophysics
Carboxypeptidases
Biochemistry
Hydrolysis
Animals
Enzyme kinetics
Binding site
Pancreas
Molecular Biology
chemistry.chemical_classification
Binding Sites
biology
Chemistry, Physical
Chemistry
Active site
Substrate (chemistry)
Cell Biology
Models, Structural
Enzyme
biology.protein
Carboxypeptidase A
Cattle
Peptides
Subjects
Details
- ISSN :
- 0006291X
- Volume :
- 29
- Database :
- OpenAIRE
- Journal :
- Biochemical and Biophysical Research Communications
- Accession number :
- edsair.doi.dedup.....8fc281230839a7647087314c42dec692