Histidine aminotransferase activity in Streptomyces tendae and its correlation with nikkomycin production

Streptomyces tendae Tü901 produces nikkomycins belonging to the nucleoside peptide antibiotics. Mutants defective in histidine catabolism were isolated and characterized with regard to their histidine ammonium-lyase activity and antibiotic synthesis. In the histidine ammonialyase-negative mutant hut-11 which was unimpaired in nikkomycin production histidine aminotransferase activity was detected as an additional histidine metabolizing enzyme. A protein exhibiting histidine aminotransferase activity could be demonstrated on non-denaturing gels of hut-11 crude extracts. Using optimized assay conditions, histidine aminotransferase activity was investigated in the strain hut-11 during growth in nikkomycin production medium. Maximal activity was reached at the end of exponential growth prior to nikkomycin production. In the presence of bromopyruvate, an effective inhibitor of histidine aminotransferase activity in vitro, production of nikkomycin Z and X was markedly reduced in hut-11.