Studies on the Structure of the Primary Oxidation Product Formed from Tetrahydropteridines during Phenylalanine Hydroxylation
نویسنده
چکیده
The enzymatic conversion of phenylalanine to tyrosine requires a reduced pteridine cofactor (1, 2). This requirement can be met by a naturally occurring compound with structure closely related to biopterin and sepia pteridine (3) or by certain synthetic pteridines such as 2-amino-4-hydroxy-6,7-dimethyl5,6,7 ,%tetrahydropteridine (4). In the presence of the latter compound, the hydroxylation reaction proceeds according to Equations 1 and 2 (4).
منابع مشابه
Studies on the Mechanism of the Enzymatic of Phenylalanine to Tyrosine C onversion
At least two enzymes,’ one obtained from rat liver and the other from sheep liver extracts, as well as a nonprotein cofactor of unknown structure (2) have been shown to be involved in the reaction. Although some progress has been made in the purification of these three components, the role of the cofactor, of the enzymes, and even that of the reduced pyridine nucleotide in the enzymatic convers...
متن کاملThe inactivation of phenylalanine hydroxylase by 2-amino-4-hydroxy-6,7-dimethyltetrahydropteridine and the aerobic oxidation of the latter. The effects of catalase, dithiothreitol and reduced nicotinamide-adenine dinucleotide.
1. Phenylalanine hydroxylase is inhibited by its cofactor, 6,7-dimethyltetrahydropterin. The rate of inactivation, which is irreversible, increases with the concentration of cofactor. 2. Catalase, in sufficient amount relative to cofactor, prevents this inactivation. More tyrosine is formed in the presence of added catalase. 3. Dithiothreitol in the presence of liver extract also prevents inact...
متن کاملEvidence for the formation of the 4a-carbinolamine during the tyrosine-dependent oxidation of tetrahydrobiopterin by rat liver phenylalanine hydroxylase.
In the presence of phenylalanine and molecular oxygen, activated phenylalanine hydroxylase catalyzes the oxidation of tetrahydrobiopterin. The oxidation of this tetrahydropterin cofactor also proceeds if the substrate, phenylalanine, is replaced by its product, tyrosine, in the initial reaction mixture. These two reactions have been defined as coupled and uncoupled, respectively, because in the...
متن کاملA NOVEL QUINONE DIMETHIDE FORMED BY AERIAL OXIDATION OF 1,2,3,4,5,6,7,8- OCTAHYDRO-9,lO-DIHYDROXY1,-5 ANTHRACENEDIONE
During the development of a new regiospecific synthetic methodology for 1,5 dihydroxy- 9,lO-anthraquinone, it was observed that (anthrufin) preparative TLC of 1,2,3,4,5,6,7,8-octahydro-9,lO-dihyd roxy- 1,5-anthracenedione on silica gel produced a well-defined 1:l complex of the dione and an aerial oxidation product of it, the quinone dimethide 1,2,3,4,5,6,7- hexahydro-9,lO-dihydroxy-1 ,5-...
متن کاملThe hydroxylation of phenylalanine and tyrosine: a comparison with salicylate and tryptophan.
The hydroxylation of phenylalanine by the Fenton reaction and gamma-radiolysis yields 2-hydroxy-, 3-hydroxy-, and 4-hydroxyphenylalanine (tyrosine), while the hydroxylation of tyrosine results in 2,3- and 3,4-dihydroxyphenylalanine (dopa). Yields are determined as a function of pH and the presence or absence of oxidants. During gamma-radiolysis and the Fenton reaction the same hydroxylated prod...
متن کامل