ISSN:
0006-3592
Keywords:
Chemistry
;
Biochemistry and Biotechnology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
,
Process Engineering, Biotechnology, Nutrition Technology
Notes:
A cephalosporin acetylesterase produced by Bacillus subtilis catalyzes the deacetylation of 7-aminocephalosporanic acid (7-ACA). Previous reports from our laboratory described the kinetic constants that characterize the reaction: Km = 2.8 × 10-3M, Kia acetate = 5 × 10-2M, and Kid deacetyl-7-ACA = 3.6 × 10-2M. These constants were used to predict the time course of the reaction using the following equation for dual competitive product inhibition. \documentclass{article}\pagestyle{empty}\begin{document}$$ \frac{{dS_t}}{{dt}} = \frac{{- V_{\max}}}{{1 + \left({K_m /S_t} \right)\left({1 + A_t /K_{{\rm ia}} + D_t /K_{{\rm id}}} \right)}} $$\end{document} where St = mg/ml 7-ACA, At = mg/ml acetate, Dt = mg/ml deacetyl-7-ACA. The predicted time course closely matched the time course measured experimentally. The equation also was solved without the inhibition terms and the solution indicated that product inhibition caused about a 30% increase in the time required for complete (〉97%) hydrolysis of a 24 mg/ml 7-ACA solution. The esterase was immobilized by containment within an ultrafiltration device. With this technique the enzyme was reused 20 times over an 11 day span to deacetylate 7-ACA solutions containing 4 to 24 mg/ml 7-ACA. The specific activity after the 20th use was the same as the activity prior to the first use, indicating little enzyme inactivation occurred.
Additional Material:
3 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/bit.260180802
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