2,5-Diamino-6-hydroxy-4-(5-phosphoribosylamino)pyrimidine explained

2,5-diamino-6-hydroxy-4-(5-phosphoribosylamino)pyrimidine is a metabolite in the purine metabolism, formed by the hydrolysis of GTP by GTP cyclohydrolase II.^[1] Alternatively two separate enzymes can carry out this reaction, initially GTP cyclohydrolase IIa hydrolyses the 8,9 bond to form 2-Amino-5-formylamino-6-(5-phospho-D-ribosylamino)pyrimidin-4(3H)-one,^[2] followed by de-formylation by 2-amino-5-formylamino-6-ribosylaminopyrimidin-4(3H)-one 5'-monophosphate deformylase.^[3] 2,5-diamino-6-hydroxy-4-(5-phosphoribosylamino)pyrimidine is deaminated by Diaminohydroxyphosphoribosylaminopyrimidine deaminase to form 5-amino-6-(5-phosphoribosylamino)uracil.^[4]

Notes and References

1. Foor F, Brown GM . 1975 . Purification and properties of guanosine triphosphate cyclohydrolase II from Escherichia coli . J. Biol. Chem. . 250 . 3545 - 51 . 235552 . 9. 10.1016/S0021-9258(19)41549-4 . free .
2. Graham DE, Xu H, White RH . 2002 . A member of a new class of GTP cyclohydrolases produces formylaminopyrimidine nucleotide monophosphates . Biochemistry . 41 . 15074 - 84 . 12475257 . 10.1021/bi0268798 . 50 .
3. An iron(II) dependent formamide hydrolase catalyzes the second step in the archaeal biosynthetic pathway to riboflavin and 7,8-didemethyl-8-hydroxy-5-deazariboflavin . Grochowski, L.L. . Xu, H. . White, R.H. . amp . Biochemistry . 2009 . 48 . 4181–4188 . 19309161 . 10.1021/bi802341p . 19.
4. Burrows RB, Brown GM . 1978 . Presence of Escherichia coli of a deaminase and a reductase involved in biosynthesis of riboflavin . J. Bacteriol. . 136 . 657 - 67 . 30756 . 2 . 10.1128/JB.136.2.657-667.1978 . 218591.