Pterin biosynthesis, scheme

There are a number of studies on the biosynthesis of various pteridines, i.e., xanthopterin (65), isoxanthopterin (67), erythropterin (73), leucopterin (68), and pterin (62) (509-511). The most important intermediate of the proposed biosynthetic pathway from guanosine triphosphate (GTP) (604) seems to be di-hydroneopterin triphosphate (H2-NTP) (605), however, because evidence has recently been accumulated indicating that pteridines such as biopterin (70), sepiapterin (81), and drosopterins (87) are synthesized from GTP (604) by way of H2-NTP (605) (Scheme 76) (5/2). 

The enzymes in the zebra fish pathway are presumably very similar to those of other vertebrates. However a completely different type of GTP cyclohydrolase has been identified in the hyperthermophilic euryarchaeon, Methanococcus jannashii <2002B15074>. This enzyme, in purified recombinant form, produced as a stable end product 2-amino-5-formylamino-6-ribofuranosylamino-4(3//)-pyrimidinone monophosphate, a compound that is an intermediate in the action of normal GTP cyclohydrolases. The biosynthesis of the incorporation of the pterin into methanopterin in Methanobacterium thermoautotrophicum has been proposed to occur via substitution of 7,8-dihydro-6-hydroxymethylpterin diphosphate 227 (Scheme 44) <1998BBA257>. 

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