Oxidation of nicotinic acid by a Bacillus species: source of oxygen atoms for the hydroxylation of nicotinic acid and 6-hydroxynicotinic acid.

Three types of evidence are presented to show that the enzymes that hydroxylate nicotinic acid to 2,6-dihydroxynicotinic acid use water as a source of oxygen atoms. (18)O is incorporated into the products from H(2) (18)O. Molecular oxygen acts as a terminal electron acceptor, one-half molecule being consumed per molecule of hydroxyl groups incorporated. An external electron acceptor is required for activity in purified preparations.