Affiliation:
1. Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, Pennsylvania 16802
Abstract
ABSTRACT
We isolated a gram-positive, halotolerant psychrophile from a hypersaline pond located on the McMurdo Ice Shelf in Antarctica. A phylogenetic analysis of the 16S rRNA gene sequence of this organism showed that it is a member of the genus
Planococcus
. This assignment is consistent with the morphology and physiological characteristics of the organism. A gene encoding a β-galactosidase in this isolate was cloned in an
Escherichia coli
host. Sequence analysis of this gene placed it in glycosidase family 42 most closely related to an enzyme from
Bacillus circulans
. Even though an increasing number of family 42 glycosidase sequences are appearing in databases, little information about the biochemical features of these enzymes is available. Therefore, we purified and characterized this enzyme. The purified enzyme did not appear to have any metal requirement, had an optimum pH of 6.5 and an optimum temperature of activity at 42°C, and was irreversibly inactivated within 10 min when it was incubated at 55°C. The enzyme had an apparent
K
m
of 4.9 μmol of
o
-nitrophenyl-β-
d
-galactopyranoside, and the
V
max
was 467 μmol of
o
-nitrophenol produced/min/mg of protein at 39°C. Of special interest was the finding that the enzyme remained active at high salt concentrations, which makes it a possible reporter enzyme for halotolerant and halophilic organisms.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Cited by
79 articles.
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