A pyridoxal 5'-phosphate enzyme. The enzyme from the bacterium Amycolatopsis mediterranei participates in the pathway for rifamycin B biosynthesis. The enzyme also functions as a transaminase earlier in the pathway, producing UDP-alpha-D-kanosamine .
enzyme is part of the aminoshikimate pathway of formation of 3-amino-5-hydroxybenzoic acid, the precursor of ansamycin and other antibiotics. Nitrogenous precursor Kanosamine is phosphorylated and converted into 1-deoxy-1-imino-erythrose 4-phosphate, the substrate for the formation of 3,4-dideoxy-4-amino-D-arabino-seduheptulosonic acid 7-phosphate. This is converted via 5-deoxy-5-aminodehydroquinic acid and 5-deoxy-5-aminodehydroshikimic acid into 3-amino-5-hydroxybenzoic acid. 3-amino-5-hydroxybenzoic acid synthase seems to have two catalytic functions. As a homodimer, it catalyzes the last reaction in the pathway, the aromatization of 5-deoxy-5-aminodehydroshikimic acid, and at the beginning of the pathway in a complex with the oxidoreductase RifL it catalyzes the transamination of UDP-3-keto-D-glucose
enzyme is a dimer containing one molecule of pyridoxal phosphate per subunit. The enzyme-bound pyridoxal phosphate forms a Schiffs 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
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in complex with pyridoxal 5'-phosphate and with pyridoxal 5'-phosphate and inhibitor gabaculine. The overall fold of is similar to that of the aspartate aminotransferase family of PLP-dependent enzymes, with a large domain containing a seven-stranded beta-sheet surrounded by alpha-helices and a smaller domain consisting of a four-stranded antiparallel beta-sheet and four alpha-helices. The uninhibited form of the enzyme shows the cofactor covalently linked to residue Lys188 in an internal aldimine linkage. On binding the inhibitor, gabaculine, the internal aldimine linkage is broken, and a covalent bond is observed between the cofactor and inhibitor. The active site is composed of residues from two subunits, indicating that the enzyme is active as a dimer