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B6db references: 98165773

type Journal Article
authors Kim, C.G., Yu, T.W., Fryhle, C.B., Handa, S.; Floss, H.G.
title 3-Amino-5-hydroxybenzoic Acid Synthase, the Terminal Enzyme in the Formation of the Precursor of mC7N Units in Rifamycin and Related Antibiotics
journal J Biol Chem.
ui 98165773
year (1998)
volume 273
number 11
pages 6030-6040
abstract The biosynthesis of ansamycin antibiotics, like rifamycin B, involves formation of 3-amino-5-hydroxybenzoic acid (AHBA) by a novel variant of the shikimate pathway. AHBA then serves as the starter unit for the assembly of a polyketide which eventually links back to the amino group of AHBA to form the macrolactam ring. The terminal enzyme of AHBA formation, which catalyzes the aromatization of 5-deoxy-5-amino-3-dehydroshikimic acid, has been purified to homogeneity from Amycolatopsis mediterranei, the encoding gene has been cloned, sequenced, and overexpressed in Escherichia coli. The recombinant enzyme, a (His)6 fusion protein, as well as the native one, are dimers containing one molecule of pyridoxal phosphate per subunit. Mechanistic studies showed that the enzyme-bound pyridoxal phosphate forms a Schiff's base with the amino group of 5-deoxy-5-amino-3-dehydroshikimic acid and catalyzes both an alpha, beta-dehydration and a stereospecific 1,4-enolization of the substrate. Inactivation of the gene encoding AHBA synthase in the A. mediterranei genome results in loss of rifamycin formation; production of the antibiotic is restored when the mutant is supplemented with AHBA.
last changed 2014/02/20 12:22

B6db references