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J. Bacteriol., Dec 1996, 6778-6781, Vol 178, No. 23
O Kwon, DK Bhattacharyya and R Meganathan
The coenzyme A (CoA)- and ATP-dependent conversion of o-succinylbenzoic
acid [OSB; 4-(2'-carboxyphenyl)-4-oxobutyric acid], to o-
succinylbenzoyl-CoA is carried out by the enzyme o-succinylbenzoyl-CoA
synthetase. o-Succinylbenzoyl-CoA is a key intermediate in the biosynthesis
of menaquinone (vitamin K2) in both gram-negative and gram- positive
bacteria. The enzyme has been overexpressed and purified to homogeneity.
The purified enzyme was found to have a native molecular mass of 185 kDa as
determined by gel filtration column chromatography on Sephacryl S-200.
Sodium dodecyl sulfate-polyacrylamide gel electrophoresis established a
subunit molecular mass of 49 kDa. Thus, the enzyme is a homotetramer. The
enzyme showed a pH optimum of 7.5 to 8.0 and a temperature optimum of 30 to
40 degrees C. The Km values for OSB, ATP, and CoA were 16, 73.5, and 360
microM, respectively. Of the various metal ions tested, Mg2+ was found to
be the most effective in stimulating the enzyme activity. Studies with
substrate analogs showed that neither benzoic acid nor benzoylpropionic
acid (succinylbenzene) is a substrate for the enzyme. Thus, it appears that
both the benzoyl carboxyl group and the succinyl side chain are required
for activation of the aliphatic carboxyl group.
Copyright © 1996, American Society for Microbiology
Menaquinone (vitamin K2) biosynthesis: overexpression, purification, and properties of o-succinylbenzoyl-coenzyme A synthetase from Escherichia coli
Department of Biological Sciences, Northern Illinois University, DeKalb 60115-2861, USA.
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