The Mechanism of Cofactor Regeneration During Phenylalanine Hydroxylation
Although the ability of the liver to convert phenylalanine to tyrosine has been known since 19131, characterization of the components of the system did not begin until the mid 1950’s. Tetrahydrobiopterin was identified as the cofactor for the hydroxylase reaction2, which uses molecular oxygen as the source of the new hydroxyl group, Figure 1. It was first thought that only one other enzyme, dihydropteridine reductase (DHPR), was involved in the overall process. This converts the oxidized form of cofactor, a quinoid dihydropterin3, back to the starting tetrahydrobiopterin at the expense of NADH allowing cofactor to be used catalytically. The clinical symptoms of patients with a deficiency of DHPR have shown that cofactor regeneration is essential4.
KeywordsEntropy Tyrosine Ketone Dehydration Folate
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