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Abstract

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  2. Abstract
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The isopenicillin-N acyltransferase of Penicillium chrysogenum catalyzes the conversion of the biosynthetic intermediate isopenicillin N to the hydrophobic penicillins. The isopenicillin-N acyltransferase copurified with the acyl-CoA:6-aminopenicillanic acid (6-APA) acyltransferase activity which transfers an acyl residue from acyl-CoA derivatives (e.g. phenylacetyl-CoA, phenoxyacetyl-CoA) to 6-APA. Other thioesters of phenylacetic acid were also used as substrates. An amino acid sequence similar to that of the active site of thioesterases was found in the isopenicillin-N acyltransferase, suggesting that this site is involved in the transfer of phenylacetyl residues from phenylacetyl thioesters. Purified isopenicillin-N acyltransferase also showed isopenicillin-N amido-hydrolase, penicillin transacylase and penicillin amidase activities. The isopenillin-N amidohydrolase (releasing 6-APA) showed a much lower specific activity than the isopenicillin-N acyltransferase of the same enzyme preparation, suggesting that in the isopenicillin-N acyltransferase reaction the 6-APA is not released and is directly converted into benzylpenicillin. Penicillin transacylase exchanged side chain between two hydrophobic penicillin molecules; or between one penicillin molecule and 6-APA. The penicillin amidase activity is probably the reverse of the biosynthetic acyl-CoA:6-APA acyltransferase. Four P. chrysogenum mutants deficient in acyl-CoA:6-APA acyltransferase lacked the other four related activities. Transformation of these mutants with the penDE gene restored all five enzyme activities.

Abbreviations
AAT

acyl-CoA:6-aminopenicillanic acid acyltransferase

6-APA

6-aminopenicillanic acid

CIHgBzOH

4-chloromercuribenzoic acid

IAT

acyl-CoA:isopenicillin-N acyltransferase

IPN

isopenicillin N

npe

mutation which results in nonproduction of penicillin

pcbC

gene encoding isopenicillin-N synthase

penDE

gene encoding isopenicillin-N acyltransferase

PhMeSO2F

phenylmethylsulfonyl fluoride

REFERENCES

  1. Top of page
  2. Abstract
  3. REFERENCES