    4.1.99.22 | GTP + S-adenosyl-L-methionine + reduced electron acceptor = (8S)-3',8-cyclo-7,8-dihydroguanosine 5'-triphosphate + 5'-deoxyadenosine + L-methionine + oxidized electron acceptor |
proposed mechanism for the MoaA/MoaC-catalyzed reaction, detailed overview. MoaA/MoaC catalyzes a remarkable rearrangement reaction in which the C8 of GTP is inserted into the ribose C2'-C3' bond, several radical reaction intermediates, mass spectrometric analysis |
727684 |
| 4.1.99.22 | GTP + S-adenosyl-L-methionine + reduced electron acceptor = (8S)-3',8-cyclo-7,8-dihydroguanosine 5'-triphosphate + 5'-deoxyadenosine + L-methionine + oxidized electron acceptor |
the N-terminal [4Fe-4S] cluster is likely to be responsible for the reductive cleavage of SAM to the 5'-deoxyadenosyl radical and L-methionine and the second cluster binds to N1 of GTP. Upon generation of the 5'-deoxyadenosyl radical, GTP is transformed into (2-amino-7-hydroxy-4,6-dioxo-4,5,5a,6,7,8,9a,10-octahydro-3H-pyrano[3,2-g]pteridin-8-yl)methyl triphosphate via a complex rearrangement reaction where the C8 atom of the purine is inserted between the C2' and the C3' atoms of the ribose moiety. MoaC then catalyzes the intramolecular cyclization reaction of (2-amino-7-hydroxy-4,6-dioxo-4,5,5a,6,7,8,9a,10-octahydro-3H-pyrano[3,2-g]pteridin-8-yl)methyl triphosphate to (2-amino-7-hydroxy-4,6-dioxo-4,5,5a,6,7,8,9a,10-octahydro-3H-pyrano[3,2-g]pteridin-8-yl)methyl triphosphate which is oxidized to 2-amino-6-(2,5-dihydroxy-2-oxido-1,3,2-dioxaphosphinane-4-carbonyl)pteridin-4(3H)-one prior to analysis because of the instability of (2-amino-7-hydroxy-4,6-dioxo-4,5,5a,6,7,8,9a,10-octahydro-3H-pyrano[3,2-g]pteridin-8-yl)methyl triphosphate |
727013 |
