GTP cyclohydrolase
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GTP cyclohydrolases are enzymes that catalyze imidazole ring opening of guanosine triphosphate (GTP).[1] This reaction is the committed step in the biosynthesis of multiple coenzymes (such as riboflavin and folate), tRNA bases, and the phytotoxin toxoflavin.[1] Several GTP cyclohydrolases exist, which sometimes synthesize different products for different purposes:
- GTP cyclohydrolase I, part of the tetrahydrobiopterin, tetrahydrofolate, queuosine and other biosynthetic pathways[1]
- GTP cyclohydrolase Ia,
- GTP cyclohydrolase Ib, part of the tetrahydrobiopterin, tetrahydrofolate, queueosine and other biosynthetic pathways[1]
- GTP cyclohydrolase II, part of the riboflavin and toxoflavin biosynthetic pathways[1]
- GTP cyclohydrolase IIa[2] (or GTP cyclohydrolase III[3]), part of the riboflavin and deazaflavin cofactor biosynthetic pathways[1]
- GTP cyclohydrolase IV
- GTP cyclohydrolase MptA, GTP cyclohydrolase Ib paralog[1]
These enzymes require divalent cations for catalysis.[1]
References
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