Stabilization ofEscherichia coli penicillin G acylase by polyethylene glycols against thermal inactivation |
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Authors: | Dilek Kazan Altan Erarslan |
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Institution: | (1) Scientific and Technical Research Council of Turkey, Marmara Research Centre, Research Institute for Genetic Engineering and Biotechnology, Laboratory of Enzyme and Fermentation Technology, P.O. Box 21, 41470 Gebze-Kocaeli, Turkey;(2) Kocaeli University, Faculty of Arts and Sciences, Department of Chemistry, Section of Biochemistry, Izmit-Kocaeli, Turkey |
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Abstract: | The effects of five polyethylene glycol (PEG) compounds of different molecular weight on the thermal stability of penicillin
G acylase (PGA) obtained from a mutant ofEscherichia coli ATCC 11105 have been investigated. The molecular weights of PEG compounds were 400, 4000, 6000, 10,000, and 15,000. The thermal
inactivation mechanisms of both native and PEG-containing PGA were considered to obey first order inactivation kinetics during
prolonged heat treatments. Optimal concentrations of PEGs at molecular weights of 400,4000, 6000,10,000, and 15,000 were found
to be 250,150,150,100, and 50 mM, respectively. The greatest enhancement of thermostability was observed with PEG 4000 and
PEG 6000, as a nearly 20-fold increase above 50°C. PGA showed almost the same temperature activity profile and optimal temperature
values both in the presence and absence of PEG. The addition of PEGs did not cause any change in the optimal temperature value
of PGA, but the parametersV
m
,K
m
, the activation energy, and thek
cat
values of enzyme were markedly decreased because of the mixed inhibition by PEG compounds. The type of inhibition was found
to be hyperbolic uncompetitive. |
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Keywords: | Escherichia coli penicillin G acylase polyethylene glycols irreversible enzyme inactivation kinetics hyperbolic type mixed inhibition of enzyme enzyme thermostabilization |
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