A novel epimerization system in fungal secondary metabolism involved in the conversion of isopenicillin N into penicillin N in Acremonium chrysogenum

The epimerization step that converts isopenicillin N into penicillin N during cephalosporin biosynthesis has remained uncharacterized despite its industrial relevance. A transcriptional analysis of a 9-kb region located downstream of the pcbC gene revealed the presence of two transcripts that corres...

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Bibliographic Details
Published in:The Journal of biological chemistry 2002-11, Vol.277 (48), p.46216-46225
Main Authors: Ullan, Ricardo V, Casqueiro, Javier, Banuelos, Oscar, Fernandez, Francisco J, Gutierrez, Santiago, Martin, Juan F
Format: Article
Language:English
Subjects:
Acremonium - enzymology
Acremonium - metabolism
Amino Acid Sequence
Animals
Bacterial Proteins - chemistry
Bacterial Proteins - genetics
Bacterial Proteins - metabolism
Base Sequence
Chromatography, High Pressure Liquid
DNA Primers
Humans
Molecular Sequence Data
Penicillins - metabolism
Racemases and Epimerases - metabolism
Rats
Sequence Homology, Amino Acid
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Summary:The epimerization step that converts isopenicillin N into penicillin N during cephalosporin biosynthesis has remained uncharacterized despite its industrial relevance. A transcriptional analysis of a 9-kb region located downstream of the pcbC gene revealed the presence of two transcripts that correspond to the genes named cefD1 and cefD2 encoding proteins with high similarity to long chain acyl-CoA synthetases and acyl-CoA racemases from Mus musculus, Homo sapiens, and Rattus norvegicus. Both genes are expressed in opposite orientations from a bidirectional promoter region. Targeted inactivation of cefD1 and cefD2 was achieved by the two-marker gene replacement procedure. Disrupted strains lacked isopenicillin N epimerase activity, were blocked in cephalosporin C production, and accumulated isopenicillin N. Complementation in trans of the disrupted nonproducer mutant with both genes restored epimerase activity and cephalosporin biosynthesis. However, when cefD1 or cefD2 were introduced separately into the double-disrupted mutant, no epimerase activity was detected, indicating that the concerted action of both proteins encoded by cefD1 and cefD2 is required for epimerization of isopenicillin N into penicillin N. This epimerization system occurs in eukaryotic cells and is entirely different from the known epimerization systems involved in the biosynthesis of bacterial beta-lactam antibiotics.
ISSN:0021-9258
DOI:10.1074/jbc.M207482200