Family C45


Summary Holotypes Alignment Tree Genomes Structure Literature

Summary for family C45

Family type peptidaseC45.001 - acyl-coenzyme A:6-aminopenicillanic acid acyl-transferase precursor (Penicillium chrysogenum), MEROPS Accession MER0004220 (peptidase unit: 103-357)
Content of familyPeptidase family C45 contains autolytic endopeptidases.
History Identifier created: MEROPS 5.00 (20 April 2000)
Acyl-coenzyme A:6-aminopenicillanic-acid-acyltransferase is the last enzyme in the penicillin biosynthetic pathway. It is synthesized as a precursor and activated autolytically to a two-chain form. The proteolytic activity is confined to the acyl-coenzyme A:6-aminopenicillanic-acid-acyltransferase precursor (C45.001).
Catalytic typeCysteine
Active site residuesC103 
Active siteThe active site cysteine is Cys103, which becomes the new N-terminus following cleavage (see the Alignment). Mutation of this residue prevents autolysis (Tobin et al., 1995). It is not known whether Cys103 is involved in the acyltransferase activity of the mature protein.
Activities and specificitiesPeptidase activity is confined to the precursor protein. Once cleavage occurs at the Gly102Cys bond, no further peptidase activity remains (Aplin et al., 1993; Tobin et al., 1993). The mature acyltransferase is a two-chain molecule.
Molecular structureCrystals of acyl-coenzyme A:6-aminopenicillanic-acid-acyltransferase have been grown (Hensgens et al., 2002), but no tertiary structure has been determined for any member of family C45. The family is included in clan PB because the nucleophile is at the N-terminus of the mature protein, as it is in active components of the proteasome (XT01-001).
Basis of clan assignmentThe active site residue for members of this family and family T1 is C-terminal to the autolytic cleavage site.
Distribution of family Bacteria details  
Archaea details  
Protozoa details  
Fungi details  
Plants details  
Animals details  
Viruses -  
Biological functionsFollowing activation by its autolysis, acyl-coenzyme A:6-aminopenicillanic-acid-acyltransferase converts isopenicillin N to penicillin G, substituting alpha-aminoadipic acid on the penicillin ring for phenylacetic acid. Phenyl-acetyl-CoA or phenoxyacetyl-CoA are cofactors in the reaction. Acyltransferase activity is in the C-terminal 29-kDa chain.
ReviewsSmith (2004)
Statistics for family C45Sequences:1106
Identifiers with PDB entries:1
Downloadable files Sequence library (FastA format)
Sequence alignment (FastA format)
Phylogenetic tree (Newick format)
Peptidases and Homologues MEROPS ID Structure
acyl-coenzyme A:6-aminopenicillanic acid acyl-transferase precursorC45.001Yes
CG12120 protein (Drosophila melanogaster)C45.A01-
family C45 non-peptidase homologuesnon-peptidase homologue-
family C45 unassigned peptidasesunassigned-