%0 Journal Article %A Castro, Jos M. %A Liras, Paloma %A Laz, Leonila %A Corts, Jess %A Martn, Juan F. %T Purification and Characterization of the Isopenicillin N Synthase of Streptomyces lactamdurans %D 1988 %J Microbiology, %V 134 %N 1 %P 133-141 %@ 1465-2080 %R https://doi.org/10.1099/00221287-134-1-133 %I Microbiology Society, %X The isopenicillin N synthase (cyclase) of Streptomyces lactamdurans (syn. Nocardia lactamdurans) has been purified to near homogeneity as judged by SDS-PAGE and isoelectric focusing. This enzyme catalyses the oxidative cyclization of the tripeptide δ-(l-α-aminoadipyl)-l-cysteinyl-d-valine to isopenicillin N. The enzyme required DTT, Fe2+ and oxygen and it was greatly stimulated by ascorbic acid. It was strongly inhibited by Co2+, Zn2+ and Mn2+. Optimal pH and temperature were 7·0 and 25 °C (with the assay conditions used), respectively. The apparent K m of isopenicillin N synthase for δ-(l-α-aminoadipyl)-l-cysteinyl-d-valine was 0·18 mm. The enzyme is a monomer with an M r of 26500 ± 1000 and a pI of 6.55. %U https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-134-1-133