Purification and characterization of a new type of acid carboxypeptidase from Aspergillus
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Abstract:

Abstract1.1.|This paper reports the purification and characterization of a new type of acid carboxypeptidase from Aspergillus. The highly purified enzyme was found to be essentially homogeneous by such criteria as sedimentation in the ultracentrifuge and disc electrophoreses on polyacrylamide gel at pH 9.5, 8.0 and 2.3.2.2.|The enzyme has a pH optimum at pH 3.1 for Z-Glu-Tyr, pH 3.5 for Z-Tyr-Leu, pH 3.2 for Z-Gly-Pro-Leu-Gly, and pH 3.5 for Bz-Gly-Lys.The Km and νmax values for Z-Glu-Tyr at pH 3.1 and 30° are 1.25 · 10−3 M and 1.9 · 104 μmoles tyrosine per min for A280 nm, the values for Z-Tyr-Leu at pH 3.5 and 30° are 1.0–10−3 M and 1.64 · 105 μmoles leucine/min for A280 nm, and the values for Bz-Gly-Lys at pH 3.5 and 30° are 4.0 · 10−3 M and 5.5 · 102 μmoles lysine per min for A280 nm.The specificity of the enzyme was investigated for a wider range of substrates at the acid end of the pH spectrum and the carboxypeptidase-like activity was confirmed.3.3.|According to the Yphantis' procedure, the molecular weight of the enzyme at 0.2 ionic strength was found to be 139 000. The sedimentation constant was determined to be 7.3 S. According to the gel filtration method, molecular weight values 155 000 for the larger form or polymer and 51 000 for the smaller form or monomer were obtained in the absence of NaCl, and a molecular weight value of 135 000 was obtained in the presence of 0.2 M NaCl.4.4.|The enzymatic activity was inhibited by DFP at pH 6.0 and 0°, and was not affected by EDTA at pH 5.2 and 5°.

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