3-Amino-5-hydroxybenzoic acid synthase, the terminal enzyme in the formation of the precursor of mC7N units in rifamycin and related antibiotics.

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.

• Authors: C G Kim, T W Yu, C B Fryhle, S Handa, H G Floss
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 273 Issue 11 Pg. 6030-40 (Mar 13 1998) ISSN: 0021-9258 [Print] United States
• PMID: 9497318 (Publication Type: Comparative Study, Journal Article, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• 5-deoxy-5-amino-3-dehydroshikimic acid
• Aminobenzoates
• Cyclohexanecarboxylic Acids
• Hydroxybenzoates
• Recombinant Proteins
• Rifamycins
• Shikimic Acid
• gabaculine
• Pyridoxal Phosphate
• Pyridoxamine
• 3-amino-5-hydroxybenzoic acid
• Transaminases
• 3-amino-5-hydroxybenzoic acid synthase
• Hydro-Lyases
• pyridoxamine phosphate

Topics

• Actinobacteria (enzymology, genetics)
• Actinomycetales (enzymology, genetics)
• Amino Acid Sequence
• Aminobenzoates (metabolism)
• Base Sequence
• Cloning, Molecular
• Cyclohexanecarboxylic Acids (pharmacology)
• Escherichia coli (genetics)
• Evolution, Molecular
• Hydro-Lyases (classification, genetics, isolation & purification, metabolism)
• Hydroxybenzoates
• Molecular Sequence Data
• Phylogeny
• Pyridoxal Phosphate (metabolism)
• Pyridoxamine (analogs & derivatives, metabolism)
• Recombinant Proteins (isolation & purification, metabolism)
• Restriction Mapping
• Rifamycins (biosynthesis)
• Sequence Analysis, DNA
• Sequence Homology, Amino Acid
• Shikimic Acid (analogs & derivatives, metabolism)
• Stereoisomerism
• Substrate Specificity
• Transaminases (classification, genetics)