An enzymatic method to distinguish tetrahydrobiopterin from oxidized biopterins using UDP-glucose:tetrahydrobiopterin glucosyltransferase.

The quantitative determination of tetrahydrobiopterin (BH4) and its oxidized forms (dihydrobiopterin and biopterin) is important in searching for possible markers of neuropsychiatric and cardiovascular disorders as well as in diagnosing BH4 deficiencies. Currently, two high-performance liquid chromatography (HPLC) methods are available, although both have some limitations. We developed an enzymatic method to distinguish BH4 from the oxidized forms by employing BH4:UDP-glucose alpha-glucosyltransferase (BGluT), which catalyzes glucosyl transfer from UDP-glucose to BH4.