title: Isopenicillin N synthase and desacetoxycephalosporin C synthase activities during defined medium fermentations of Streptomyces clavuligerus: effect of oxygen and iron supplements.
abstract: When the level of dissolved oxygen was increased to saturation in defined media fermentations of Streptomyces clavuligerus, the total duration of activity of the penicillin ring cyclization enzyme, isopenicillin N synthase (IPNS), was extended by at least 20 h; however, no increase in the stability of the ring expansion enzyme, desacetoxycephalosporin C synthase (DAOCS), was observed. Consequently, the conversion of the excreted intermediate penicillin N to cephamycin C was 15-20% less efficient at this high oxygen concentration. The increased dissolved oxygen level also led to the complete loss of IPNS and DAOCS activities for 4 h during the period of fastest growth, and the rate of specific cephamycin C production fell to zero. A several hundred fold increase in the level of iron in the defined media resulted in a sixfold improvement in the rate of specific cephamycin C production after 60 h fermentation. This increased rate appeared to be due to an elevation in the in vivo activities of a number of the cephamycin biosynthetic enzymes, particularly those catalysing later pathway steps.
authors.affiliation: Department of Microbiology, University of Alberta, Edmonton, Canada.
authors.forename: M J
authors.initials: MJ
authors.lastname: Rollins
authors.forename: S E
authors.initials: SE
authors.lastname: Jensen
authors.forename: D W
authors.initials: DW
authors.lastname: Westlake
mesh_terms: D002513:Cephamycins / Q000096:biosynthesis; D003470:Culture Media; D004798:Enzymes / Q000378:metabolism*; D005285:Fermentation; D019751:Intramolecular Transferases; D007501:Iron / Q000494:pharmacology*; D007535:Isomerases / Q000378:metabolism*; D010088:Oxidoreductases; D010100:Oxygen / Q000494:pharmacology*; D046915:Penicillin-Binding Proteins; D013302:Streptomyces / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism
chemical_list: D002513:Cephamycins; D003470:Culture Media; D004798:Enzymes; D046915:Penicillin-Binding Proteins; D007501:Iron; D010088:Oxidoreductases; C038370:isopenicillin N synthetase; D007535:Isomerases; D019751:Intramolecular Transferases; C038371:deacetoxycephalosporin C synthetase; D010100:Oxygen; C024925:cephamycin C