A molybdenum-containing dehydrogenase catalyzing an unusual 2-hydroxylation of nicotinic acid

An enzyme of Ralstonia/ Burkholderia strain DSM 6920 catalyzing the initial hydroxylation of 6-methylnicotinic acid at position 2 was purified to apparent homogeneity. It also catalyzed the unusual conversion of nicotinic acid to 2-hydroxynicotinic acid and was therefore designated as nicotinic acid...

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Bibliographic Details
Published in:Applied microbiology and biotechnology 2002-04, Vol.58 (5), p.612-617
Main Authors: SCHRÄDER, T, THIEMER, B, ANDREESEN, J. R
Format: Article
Language:English
Subjects:
Acids
Bacteriology
Biological and medical sciences
Biology of microorganisms of confirmed or potential industrial interest
Biotechnology
Carboxylic acids
Dehydrogenase
Dehydrogenases
Enzymes
Fundamental and applied biological sciences. Psychology
Hydroxylation
Metabolism. Enzymes
Microbiology
Miscellaneous
Mission oriented research
Molybdenum
Molybdenum - analysis
Molybdoferredoxin - chemistry
Molybdoferredoxin - classification
Molybdoferredoxin - metabolism
Niacin - chemistry
Niacin - metabolism
Sulfur
Xanthine Oxidase - classification
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Summary:An enzyme of Ralstonia/ Burkholderia strain DSM 6920 catalyzing the initial hydroxylation of 6-methylnicotinic acid at position 2 was purified to apparent homogeneity. It also catalyzed the unusual conversion of nicotinic acid to 2-hydroxynicotinic acid and was therefore designated as nicotinic acid dehydrogenase (NDH). Native NDH had a molecular mass of 280 kDa and was composed of subunits of 75, 30 and 16 kDa. It contained molybdenum, iron, acid-labile sulfur and FAD in a ratio of 1.6:7.3:8.0:0.6 mol(-1) of native enzyme. The molybdenum cofactor was characterized as molybdopterin cytosine dinucleotide. Zinc was identified as an additional metal ion in a molar ratio of 1.8 mol mol(-1) of native enzyme. Purified NDH exhibited a maximal specific activity of 22.6 micromol nitro blue tetrazoliumchloride reduced min(-1) mg(-1) of protein, using nicotinic acid as electron donor. The apparent K(m) value for nicotinic acid was determined to be 154 microM. Pyridine-3,5-dicarboxylic acid and quinoline-3-carboxylic acid were further substrates, but exhibited significantly different activity pH optima. Several artificial electron acceptors were reduced by NDH, but no activity was detected with NAD or O(2). NDH was inactivated upon incubation with cyanide, but no loss of activity was obtained in the presence of arsenite.
ISSN:0175-7598
1432-0614
DOI:10.1007/s00253-001-0928-x