title: The enzymatic activities of GTP cyclohydrolase, sepiapterin reductase, dihydropteridine reductase and dihydrofolate reductase; and tetrahydrobiopterin content in mammalian ocular tissues and in human senile cataracts.
abstract: The enzymatic activities of GTP cyclohydrolase, sepiapterin reductase, dihydropterin reductase and dihydrofolate reductase were determined in the ocular tissues of rat, rabbit, calf and human. The enzymatic activities of the pteridine biosynthesis and the content of tetrahydropteridine (BH4) were higher in retina and ciliary body-iris as compared with lens tissue in all mammalian species tested. The activities of the pteridine synthesizing enzymes and BH4 content were decreased in human senile cataracts as compared with age-matched clear human lenses. The loss of BH4 may result in lenticular proteins more susceptible to oxidation and contribute to high molecular weight protein formation in cataracts.
mesh_terms: D000429:Alcohol Oxidoreductases / Q000378:metabolism; D000818:Animals; D001708:Biopterins / Q000031:analogs & derivatives / Q000378:metabolism*; D002386:Cataract / Q000378:metabolism*; D002417:Cattle; D002924:Ciliary Body / Q000378:metabolism; D004093:Dihydropteridine Reductase / Q000378:metabolism; D005123:Eye / Q000378:metabolism*; D006136:GTP Cyclohydrolase / Q000378:metabolism; D006801:Humans; D007498:Iris / Q000378:metabolism; D007908:Lens, Crystalline / Q000378:metabolism; D011621:Pteridines / Q000378:metabolism*; D011817:Rabbits; D051381:Rats; D012160:Retina / Q000378:metabolism; D013762:Tetrahydrofolate Dehydrogenase / Q000378:metabolism
chemical_list: D011621:Pteridines; D001708:Biopterins; D000429:Alcohol Oxidoreductases; C022630:sepiapterin reductase; D013762:Tetrahydrofolate Dehydrogenase; D004093:Dihydropteridine Reductase; D006136:GTP Cyclohydrolase; C003402:sapropterin