Glucose represses formation of delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine and isopenicillin N synthase but not penicillin acyltransferase in Penicillium chrysogenum

Abstract

The content of a-aminoadipyl-cysteinyl-valine, the first intermediate of the penicillin biosynthetic pathway, decreased when Penicillium chrysogenum was grown in a high concentration of glucose. Glucose repressed the incorporation of [14C]valine into a-aminoadipyl-cysteinyl-[14C]valine in vivo. The pool of a-aminoadipic acid increased sevenfold in control (lactose-grown) penicillin-producing cultures, coinciding with the phase of rapid penicillin biosynthesis, but this increase was very small in glucose-grown cultures. Glucose stimulated homocitrate synthase and saccharopine dehydrogenase activities in vivo and increased the incorporation of lysine into proteins. These results suggest that glucose stimulates the flux through the lysine biosynthetic pathway, thus preventing at-aminoadipic acid accumulation. The repression of a-aminoadipyl-cysteinyl-valine synthesis by glucose was not reversed by the addition of oa-aminoadipic acid, cysteine, or valine. Glucose also repressed isopenicillin N synthase, which converts a-aminoadipyl-cysteinyl-valine into isopenicillin N, but did not affect penicillin acyltransferase, the last enzyme of the penicillin biosynthetic pathway.Glucose exerts a negative control on the biosynthesis of penicillin in Penicillium chrysogenum (17,22) similar in many aspects to carbon catabolite regulation of the biosynthesis of cephalosporins in Acremonium chrysogenum (3,24) and cephamycins in Streptomyces clavuligerus (1,23) and Streptomyces lactamdurans (6). Glucose (28 to 140 mM) produces a concentration-dependent repression of the incorporation of ['4C]valine into penicillin but does not have an inhibitory effect on such incorporation by enzymes formed before glucose addition (22). The total activity of the penicillin-synthesizing enzymes in P. chrysogenum is repressed by glucose (22). Derepression of penicillin biosynthesis occurs after depletion of glucose. However, the overall biosynthetic activity of the pathway in vivo is determined by the availability of precursors of the L-a-aminoadipyl-Lcysteinyl-D-valine (ACV) tripeptide and by the activities of the (at least) three enzymes involved in penicillin biosynthesis.The first well-established intermediate in the penicillin biosynthetic pathway, ACV (2, 11), appears to be formed by a sequential condensation of the three precursor amino acids (8) (Fig. 1). ACV is then cyclized to form isopenicillin N by the action of isopenicillin N synthase, an enzyme that has been purified to near homogeneity from extracts of P. chrysogenum (19,21). In the last step of penicillin biosynthesis, the a-aminoadipyl side chain of isopenicillin N is exchanged for phenylacetic acid, which is previously activated in the form of phenylacetyl coenzyme A (CoA) (20; B. Spencer and C. Maung, Biochem. J. 118:29p-30p, 1970).The recent development of reliable assay methods to quantify the tripeptide ACV (11) and to measure the activities of isopenicillin N synthase (21) and penicillin acyltransferase (E.

Regulation of Aspergillus nidulans penicillin biosynthesis and penicillin biosynthesis genes acvA and ipnA by glucose

“…These results might also explain the observation that glucose efficiently inhibits penicillin production in P. chrysogenum only when added at an early stage of a batch fermentation (41). Later addition of glucose cannot repress the enzymes already produced, because the specific activity of IPNS is not inhibited by glucose in vitro (42). The expression of acvA, however, appears to be unaffected by glucose.…”

“…ACV and IPN are precursors of penicillin, and their synthesis is catalyzed by ACVS and IPNS. Furthermore, the specific activity of IPNS but not of ACT is reduced in cells of a penicillin production strain (AS-P-78) grown on glucose (42). These results suggested that glucose represses the formation of the enzymes ACVS and IPNS in P. chrysogenum (21,41,42).…”

“…It would thus be interesting to determine whether the same is true for the corresponding acvA gene of P. chrysogenum. In contrast to the penicillin production strain AS-P-78 of P. chrysogenum investigated by Revilla et al (42), the specific activity of the ACT of A.…”

“…The addition of glucose to the fermentation medium reduces the penicillin titer produced and the internal L-a-aminoadipic acid pool. The formation of ACV and IPN is repressed by glucose (21,41,42). ACV and IPN are precursors of penicillin, and their synthesis is catalyzed by ACVS and IPNS.…”

The isopenicillin‐N acyltransferase of Penicillium chrysogenum has isopenicillin‐N amidohydrolase, 6‐aminopenicillanic acid acyltransferase and penicillin amidase activities, all of which are encoded by the single penDE gene

“…Production of penicillin, uptake of [I4C]valine and incorporation of ['4C]valine into penicillin were carried out as described previously [19,201. ~7 1 .…”