Folates are very important cofactors that provide support for many biosynthetic reactions. The reactions depicted in this pathway include reactions that are paired with transports, within the cell, travelling intracellularly, which allows folate to be absorbed by cells, as well as the synthesis of pterines, which are used in folate synthesis. Two branches are depicted: Pterin synthesis and Folate biosynthesis. In pterin synthesis, GTP is the precursor for pterin biosynthesis. In the first reaction, GTP cyclohydrolase acts to create formamidopyrimidine nucleoside triphosphate from guanosine triphosphate, which is provided from the purine metabolism pathway. Formamidopyrimidine nucleoside triphosphate then uses GTP cyclohydrolase again to create 2,5-diaminopyrimidine nucleoside triphosphate. GTP cyclohydrolase then works with 2,5-diaminopyrimidine nucleoside triphosphate to produce 2,3-diamino-6-(5’-triphosphoryl-3’,4’-trihydroxy-2’-oxopentyl)-amino-4-oxopyrimidine, which is then converted by GTP cyclohydrolase to dihydroneopterin triphosphate. Dihydroneopterin is then transported to the mitochondria and subsequently catalyzed into dyspropterin, which then exits the mitochondria to continue pterin biosynthesis. Once having been transported from the mitochondria, dyspropterin uses sepiapterin reductase, aldose reductase and carbonyl reductase [NADPH] 1 to create 6-lactoyltetrahydropterin. This compound then undergoes 2 reactions, the first being sepiapterin reductase converting 6-lactoyltetrahydropterin into tetrahydrobiopterin, the second being 6-lactoyltetrahydropterin being converted to sepiapterin. Both branches of pterin reactions then respectively end in the creation of neopterin and dihydrobiopterin.

Pterine Biosynthesis References