A47934, a peptide antibiotic produced by Streptomyces toyocaensis, belongs to the glycopeptide class of compounds which includes ristocetin and vancomycin. Incorporation studies with radioisotope-labeled substrates indicated that tyrosine, p-hydroxyphenylglycine, p-hydroxyphenylglyoxylate, acetate, and sulfate were efficiently incorporated into A47934. This is consistent with the reported biosynthesis of other glycopeptide antibiotics. Prototrophic mutants blocked in antibiotic biosynthesis were isolated at a low frequency (0.4%) after mutagenesis. Secretor-convertor pairings of the 36 mutants obtained demonstrated that they belonged to three classes: two groups of secretor-convertor pairs and a larger group of mutants that did not make antibiotic under any condition tested. Neither the secretor-convertor studies not supplementation of the cultures with putative biosynthetic intermediates was useful in identifying the location of the biosynthetic blocks. All studies to determine the timing of the sulfate addition step in the biosynthesis indicated that the sulfate is added prior to the formation of intermediates that possess antimicrobial activity.
An enzyme was identified from Amycolatopsis orientalis as TDP‐glucose:aglycosyl vancomycin glucosyltransferase. It catalyzes the addition of a sugar onto the peptide core of the antibiotic and will use TDP‐Glc, UDP‐Glc and UDP‐Gal as co‐substrates for the transferase reaction. The peptide core of the antibiotic must have a free hydroxyl group on ring B and a specific change in the conformation of the core eliminated activity of the enzyme. Enzyme activity was optimal at pH values between 9.0 and 10.0 and a temperature of 37°C. Under these conditions, the enzyme reaction is linear for one hour. Gel filtration studies demonstrated that all the enzyme activity eluted from the column at a molecular weight of 44 kDa. This is the first report of an enzyme activity that appears to be associated with the biosynthesis of glycopeptide antibiotics.
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