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J. Bacteriol., Jun 1996, 3539-3543, Vol 178, No. 12
Z He and J Wiegel
A 3,4-dihydroxybenzoate decarboxylase (EC 4.1.1.63) from Clostridium
hydroxybenzoicum JW/Z-1T was purified and partially characterized. The
estimated molecular mass of the enzyme was 270 kDa. Sodium dodecyl
sulfate-polyacrylamide gel electrophoresis gave a single band of 57 kDa,
suggesting that the enzyme consists of five identical subunits. The
temperature and pH optima were 50 degrees C and pH 7.0, respectively. The
Arrhenius energy for decarboxylation of 3,4- dihydroxybenzoate was 32.5 kJ
. mol(-1) for the temperature range from 22 to 50 degrees C. The Km and
kcat for 3,4-dihydroxybenzoate were 0.6 mM and 5.4 x 10(3) min(-1),
respectively, at pH 7.0 and 25 degrees C. The enzyme optimally catalyzed
the reverse reaction, that is, the carboxylation of catechol to
3,4-dihydroxybenzoate, at pH 7.0. The enzyme did not decarboxylate
2-hydroxybenzoate, 3-hydroxybenzoate, 4- hydroxybenzoate,
2,3-dihydroxybenzoate, 2,4-dihydroxybenzoate, 2,5- dihydroxybenzoate,
2,3,4-trihydroxybenzoate, 3,4,5-trihydroxybenzoate, 3-F-4-hydroxybenzoate,
or vanillate. The decarboxylase activity was inhibited by 25 and 20%,
respectively, by 2,3,4- and 3,4,5- trihydroxybenzoate. Thiamine PPi and
pyridoxal 5'-phosphate did not stimulate and hydroxylamine and sodium
borohydride did not inhibit the enzyme activity, indicating that the
3,4-dihydroxybenzoate decarboxylase is not a thiamine PPi-, pyridoxal
5'-phosphate-, or pyruvoyl-dependent enzyme.
Copyright © 1996, American Society for Microbiology
Purification and characterization of an oxygen-sensitive, reversible 3,4-dihydroxybenzoate decarboxylase from Clostridium hydroxybenzoicum
Department of Microbiology, University of Georgia, Athens 30602-2605, USA.
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