PROSITE documentation PDOC00165
Isopenicillin N synthase signatures


Isopenicillin N synthase (EC (IPNS) [1,2] is a key enzyme in the biosynthesis of penicillin and cephalosporin. In the presence of oxygen, it removes iron and ascorbate, four hydrogen atoms from L-(α-aminoadipyl)-L-cysteinyl-d-valine to form the azetidinone and thiazolidine rings of isopenicillin. IPNS is an enzyme of about 330 amino-acid residues. Two cysteines are conserved in fungal and bacterial IPNS sequences; these may be involved in iron-binding and/or substrate-binding.

Cephalosporium acremonium DAOCS/DACS [3] is a bifunctional enzyme involved in cephalosporin biosynthesis. The DAOCS domain, which is structurally related to IPNS, catalyzes the step from penicillin N to deacetoxy-cephalosporin C - used as a substrate by DACS to form deacetylcephalosporin C. Streptomyces clavuligerus possesses a monofunctional DAOCS enzyme (gene cefE) [4] also related to IPNS.

We derived two signature patterns for these enzymes, centered around the conserved cysteine residues.

Last update:

May 2004 / Text revised.


Technical section

PROSITE methods (with tools and information) covered by this documentation:

IPNS_1, PS00185; Isopenicillin N synthase signature 1  (PATTERN)

IPNS_2, PS00186; Isopenicillin N synthase signature 2  (PATTERN)


1AuthorsMartin J.F.
SourceTrends Biotechnol. 5:306-308(1987).

2AuthorsChen G. Shiffman D. Mevarech M. Aharonowitz Y.
SourceTrends Biotechnol. 8:105-111(1990).

3AuthorsSamson S.M. Dotzlaf J.E. Slisz M.L. Becker G.W. van Frank R.M. Veal L.E. Yeh W.K. Miller J.R. Queener S.W. Ingolia T.D.
SourceBio/Technology 5:1207-1214(1987).

4AuthorsKovacevic S. Weigel B.J. Tobin M.B. Ingolia T.D. Miller J.R.
TitleCloning, characterization, and expression in Escherichia coli of the Streptomyces clavuligerus gene encoding deacetoxycephalosporin C synthetase.
SourceJ. Bacteriol. 171:754-760(1989).
PubMed ID2644235

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