dihydropterin

Dihydropterin is a term used in chemistry and biochemistry to describe pterin derivatives in which the pterin ring system has been partially reduced by the addition of two hydrogen atoms. It is not a single isolated compound but a class of related species that lie between pterin and more reduced forms of pterin on the redox scale. Dihydropterins share the same pteridine core but differ in substitution patterns and oxidation state.

In biological systems, dihydropterins are most often discussed in the context of pterin-based redox cycling that governs the activity of tetrahydrobiopterin (BH4), a crucial cofactor for several enzymes. BH4 participates in the hydroxylation of aromatic amino acids and in the production of nitric oxide. During catalysis BH4 can be oxidized to dihydropterin-like species. Dihydropteridine reductase (DHPR) can regenerate BH4 from these oxidized forms, typically using NADPH as an electron donor. This redox cycling helps maintain the activity of enzymes such as phenylalanine hydroxylase, tyrosine hydroxylase, and tryptophan hydroxylase.

Biochemically, dihydropterins also arise as intermediates in the de novo biosynthesis and salvage pathways of pterins. The pterin/pteridine family is widespread across organisms, and dihydropterin derivatives are studied as synthetic analogs to understand pterin chemistry and enzyme cofactors. The exact properties of a given dihydropterin derivative depend on its specific substitution pattern and oxidation state.

See also: pterin, biopterin, tetrahydrobiopterin (BH4), dihydropteridine reductase.