title: 3,4-dihydroxystyrene, a novel microbial inhibitor for phenylalanine hydroxylase and other pteridine-dependent monooxygenases.
abstract: A new microbial inhibitor for rat-liver phenylalanine hydroxylase (L-phenylalanine, tetrahydropteridine: oxygen oxidoreductase (4-hydroxylating), EC 1.14.16.1) was isolated from a culture medium of Fomes tasmanicus, and its structure was determined as 3,4-dihydroxystyrene. This compound inhibited the enzyme by 50% at a concentration of 5 X 10(-6) M and 5 X 10(-7) M, respectively, without or with preincubation at 25 degrees C for 15 min. Without preincubation, dihydroxystyrene inhibited phenylalanine hydroxylase noncompetitively with phenylalanine and a pteridine cofactor, 6,7-dimethyltetrahydropterin, and uncompetitively with oxygen. A change in kinetic properties of the inhibition was observed when the enzyme was preincubated with dihydroxystyrene; the degree of inhibition was increased, and the purely noncompetitive-type inhibition with phenylalanine changed to a mixed-type inhibition. A study concerning the structure-inhibitory activity relationship using several compounds similar to dihydroxystyrene, indicated that the catechol structure is essential and that the structure of the aliphatic side-chain affects the inhibitory potency. A similar degree of inhibition was observed using 6,7-dimethyl- or 6-methyltetrahydropterin or tetrahydrobiopterin as a cofactor. Dihydroxystyrene also inhibited other pteridine-dependent monooxygenases, tyrosine hydroxylase (EC 1.14.16.2) and tryptophan hydroxylase (EC 1.14.16.4), indicating that dihydroxystyrene is a general inhibitor for pteridine-dependent monooxygenases.
mesh_terms: D000818:Animals; D001487:Basidiomycota / Q000032:analysis*; D001667:Binding, Competitive; D008099:Liver / Q000201:enzymology; D010649:Phenylalanine / Q000494:pharmacology; D010651:Phenylalanine Hydroxylase / Q000037:antagonists & inhibitors*; D011621:Pteridines / Q000494:pharmacology; D051381:Rats; D013329:Structure-Activity Relationship; D013343:Styrenes / Q000494:pharmacology*; D013997:Time Factors; D014365:Tryptophan Hydroxylase / Q000037:antagonists & inhibitors; D014446:Tyrosine 3-Monooxygenase / Q000037:antagonists & inhibitors
chemical_list: D011621:Pteridines; D013343:Styrenes; C042750:3,4-dihydroxystyrene; D010649:Phenylalanine; C005063:2-amino-4-hydroxy-6,7-dimethyl-5,6,7,8-tetrahydropteridine; D010651:Phenylalanine Hydroxylase; D014446:Tyrosine 3-Monooxygenase; D014365:Tryptophan Hydroxylase