Transcription of the pcbAB, pcbC and penDE genes of Penicillium chrysogenum AS-P-78 is repressed by glucose and the repression is not reversed by alkaline pHs

Glucose repressed transcription of the penicillin biosynthesis genes pcbAB, pcbC and penDE when added at inoculation time to cultures of Penicillium c hrysogenum AS-P-78 but it had little repressive effect when added at 12 h a nd no effect when added at 24 or 36 h. A slight increase in the expression of pcbC and penDE (and to a smaller extent of pcbAB) was observed In glucos e-grown cultures at ph 6.8, 7.4 and 8.0 as compared with ph 6.2, but alkali ne pHs did not override the strong repression exerted by glucose. Transcrip tion of the actin gene used as control was not significantly affected by gl ucose or alkaline pHs. Repression by glucose of the three penicillin biosyn thetic genes was also observed using the lacZ reporter gene coupled to each of the three promoters in monocopy transformants with the constructions in tegrated at the pyrG locus. Glucose repression of the three genes encoding enzymes of penicillin biosynthesis therefore appears to be exerted by a reg ulatory mechanism independent from ph regulation.