title: Homologous expression of aspartokinase (ask) gene in Streptomyces clavuligerus and its hom-deleted mutant: effects on cephamycin C production.
abstract: In this study, the effect of homologous multiple copies of the ask gene, which encodes aspartokinase catalyzing the first step of the aspartate pathway, on cephamycin C biosynthesis in S. clavuligerus NRRL 3585 and its hom mutant was investigated. The intracellular pool levels of aspartate pathway amino acids accorded well with the Ask activity levels in TB3585 and AK39. When compared with the control strain carrying vector alone without any gene insert, amplification of the ask gene in the wild strain resulted in a maximum of 3.1- and 3.3-fold increase in specific, 1.7- and 1.9-fold increase in volumetric cephamycin C production when grown in trypticase soy broth (TSB) and a modified chemically defined medium (mCDM), respectively. However, expression of multicopy ask gene in a hom-deleted background significantly decreased cephamycin C yields when the cells were grown in either TSB or mCDM, most probably due to physiological disturbance resulting from enzyme overexpression and high copy number plasmid burden in an auxotrophic host, respectively.
authors.affiliation: Department of Biology, Middle East Technical University, Ankara, Turkey. ozcengiz@metu.edu.tr
authors.forename: Gülay
authors.initials: G
authors.lastname: Özcengiz
authors.forename: Sezer
authors.initials: S
authors.lastname: Okay
authors.forename: Eser
authors.initials: E
authors.lastname: Ünsaldı
authors.forename: Bilgin
authors.initials: B
authors.lastname: Taşkın
authors.forename: Paloma
authors.initials: P
authors.lastname: Liras
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Piret
mesh_terms: D001222:Aspartate Kinase / Q000235:genetics* / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D057005:Bioengineering; D002513:Cephamycins / Q000096:biosynthesis*; D003470:Culture Media / Q000378:metabolism; D018628:Gene Dosage; D015870:Gene Expression; D006715:Homoserine Dehydrogenase / Q000235:genetics* / Q000378:metabolism; D017384:Sequence Deletion; D013302:Streptomyces / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D002513:Cephamycins; D003470:Culture Media; D006715:Homoserine Dehydrogenase; D001222:Aspartate Kinase; C024925:cephamycin C