NDLI: Functional properties of beta-galactosidase from mutant strain 13 PO of Escherichia coli.

Content Provider	PubMed Central
Author	Deschavanne, P. J. Viratelle, O. M. Yon, J. M.
Abstract	The functional properties of CZP protein, a mutant deriving from wild-type beta-galactosidase (beta-D-galactoside galactohydrolase; EC 3.2.1.23) by a point mutation, were investigated. A large decrease of the specificity, as evaluated by the kcat/Km ratio, was observed, principally originated by a weaker binding of the substrates. The catalytic constants, whose values are strongly affected by the presence of divalent cations, were smaller or larger for mutant enzyme than for wild-type enzyme, depending upon the experimental conditions. Analysis of the kinetic pathway indicates, with some substrates, a change in the limiting step for the mutant enzyme compared to the wild type. Because the k'3 step is rate limiting for hydrolysis of p-nitrophenyl-beta-D-galactoside by the mutant enzyme in the absence of Mg2+ and its value is relatively small, it is possible to observe a burst of p-nitrophenol during hydrolysis. This provides conclusive evidence for the occurrence of a two-step mechanism, with a sequential release of the products.
Starting Page	1892
File Format	PDF
ISSN	10916490
e-ISSN	10916490
Journal	Proceedings of the National Academy of Sciences of the United States of America
Issue Number	4
Volume Number	75
Language	English
Publisher Date	1978-04-01
Access Restriction	Open
Subject Keyword	Research in Higher Education
Content Type	Text
Resource Type	Article
Subject	Multidisciplinary

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Functional properties of beta-galactosidase from mutant strain 13 PO of Escherichia coli.