EC - FAD-AMP lyase (cyclizing)

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IntEnz Enzyme Nomenclature


Accepted name:
FAD-AMP lyase (cyclizing)
Other names:
FMN cyclase
FAD AMP-lyase (cyclic-FMN-forming)
Systematic name:
FAD AMP-lyase (riboflavin-cyclic-4',5'-phosphate-forming)




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

Enzymes and pathways: NC-IUBMB , BRENDA , ExplorEnz , ENZYME@ExPASy , KEGG , MetaCyc , UniPathway
Structural data: CSA , EC2PDB
Gene Ontology: GO:0034012
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: 881-888 (1998). [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: 13710-13722 (2001). [PMID: 11695920]

[EC created 2002]