Open AccessGlutamine‐230 influences enzyme solubility but not catalysis in Streptomyces clavuligerus isopenicillin N synthase
Author(s) -
Loke Paxton,
Sim TiowSuan
Publication year - 1999
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.1999.tb13536.x
Subject(s) - streptomyces clavuligerus , biochemistry , glutamine , enzyme , streptomyces , streptomycetaceae , chemistry , active site , biosynthesis , stereochemistry , biology , actinomycetales , amino acid , bacteria , genetics
The conversion of δ‐( l ‐α‐aminoadipyl)‐ l ‐cysteinyl‐ d ‐valine to isopenicillin N is dependent upon the catalytic action of isopenicillin N synthase (IPNS), an important enzyme in the penicillin and cephalosporin biosynthetic pathway. Recent catalytic investigations on the conserved glutamine‐230 in the bacterial Streptomyces jumonjinensis IPNS and the corresponding glutamine‐234 in the fungal Cephalosporium acremonium IPNS showed contrasting results whereby the former was suggested to be essential for IPNS activity whereas the latter was found not to be so. In order to unravel these conflicting results, we report the site‐directed mutagenesis investigation on the corresponding glutamine‐230 in a third IPNS isozyme, which is the bacterial Streptomyces clavuligerus IPNS (scIPNS). IPNS enzymatic assays showed that catalytic activity of the mutant Q230L scIPNS was reduced but not eliminated. Moreover, the solubility of the mutant enzyme was also markedly reduced. Hence, we can conclude that glutamine‐230 in scIPNS is not essential for catalysis and correspondingly in all IPNS.