IUBMB Enzyme Nomenclature


Accepted name: PqqA peptide cyclase

Reaction: a PqqA peptide + S-adenosyl-L-methionine = a PqqA peptide with linked Glu-Tyr residues + 5'-deoxyadenosine + L-methionine

Glossary: PqqA peptide = pyrroloquinoline quinone biosynthesis protein A, a small peptide that provides the precursor for the biosynthesis of the cofactor pyrroloquinoline quinone

Other name(s): pqqE (gene name)

Systematic name: PqqA peptide:S-adenosyl-L-methionine oxidoreductase (cyclizing)

Comments: This bacterial enzyme, which is a member of the radical SAM protein family, catalyses the formation of a C-C bond between C-4 of glutamate and C-3 of tyrosine residues of the PqqA protein (which are separated by three amino acid residues). This is the first enzymic step in the biosynthesis of the bacterial enzyme cofactor pyrroloquinoline quinone (PQQ). The reaction is dependent on the presence of flavodoxin and the accessory protein PqqD.

Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, PDB, CAS registry number:


1. Wecksler, S.R., Stoll, S., Iavarone, A.T., Imsand, E.M., Tran, H., Britt, R.D. and Klinman, J.P. Interaction of PqqE and PqqD in the pyrroloquinoline quinone (PQQ) biosynthetic pathway links PqqD to the radical SAM superfamily. Chem. Commun. (Camb.) 46 (2010) 7031-7033. [PMID: 20737074]

2. Latham, J.A., Iavarone, A.T., Barr, I., Juthani, P.V. and Klinman, J.P. PqqD is a novel peptide chaperone that forms a ternary complex with the radical S-adenosylmethionine protein PqqE in the pyrroloquinoline quinone biosynthetic pathway. J. Biol. Chem. 290 (2015) 12908-12918. [PMID: 25817994]

3. Barr, I., Latham, J.A., Iavarone, A.T., Chantarojsiri, T., Hwang, J.D. and Klinman, J.P. Demonstration that the radical S-adenosylmethionine (SAM) enzyme PqqE catalyzes de novo carbon-carbon cross-linking within a peptide substrate PqqA in the presence of the peptide chaperone PqqD. J. Biol. Chem. 291 (2016) 8877-8884. [PMID: 26961875]

[EC created 2018]

Return to EC 1.21.98 home page
Return to EC 1.21 home page
Return to EC 1 home page
Return to Enzymes home page
Return to IUBMB Biochemical Nomenclature home page