IUBMB Enzyme Nomenclature


Accepted name: FAD-AMP lyase (cyclizing)

Reaction: FAD = AMP + riboflavin cyclic-4',5'-phosphate

Other name(s): FMN cyclase; FAD AMP-lyase (cyclic-FMN-forming)

Systematic name: FAD AMP-lyase (riboflavin-cyclic-4',5'-phosphate-forming)

Comments: Requires Mn2+ or Co2+. While FAD was the best substrate tested [2], the enzyme also splits ribonucleoside diphosphate-X compounds in which X is an acyclic or cyclic monosaccharide or derivative bearing an X-OH group that is able to attack internally the proximal phosphorus with the geometry necessary to form a P=X product; either a five-atom monocyclic phosphodiester or a cis-bicyclic phosphodiester-pyranose fusion. The reaction is strongly inhibited by ADP or ATP but is unaffected by the presence of the product, cFMN.

Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, CAS registry number: 208349-48-8


1. Fraiz, F.J., Pinto, R.M., Costas, M.J., Avalos, M., Canales, J., Cabezas, A. and Cameselle, J.C. Enzymic formation of riboflavin 4',5'-cyclic phosphate from FAD: evidence for a specific low-Km FMN cyclase in rat liver. Biochem. J. 330 (1998) 881-888. [PMID: 9480905]

2. Cabezas, A., Pinto, R.M., Fraiz, F., Canales, J., Gonzalez-Santiago, S., and Cameselle, J.C. Purification, characterization, and substrate and inhibitor structure-activity studies of rat liver FAD-AMP lyase (cyclizing): preference for FAD and specificity for splitting ribonucleoside diphosphate-X into ribonucleotide and a five-atom cyclic phosphodiester of X, either a monocyclic compound or a cis-bicyclic phosphodiester-pyranose fusion. Biochemistry 40 (2001) 13710-13722. [PMID: 11695920]

[EC created 2002]

Return to EC 4.6.1 home page
Return to EC 4.6 home page
Return to EC 4 home page
Return to Enzymes home page
Return to IUBMB Biochemical Nomenclature home page