منابع مشابه
Effective L-Tyrosine Hydroxylation by Native and Immobilized Tyrosinase
Hydroxylation of L-tyrosine to 3,4-dihydroxyphenylalanine (L-DOPA) by immobilized tyrosinase in the presence of ascorbic acid (AH2), which reduces DOPA-quinone to L-DOPA, is characterized by low reaction yields that are mainly caused by the suicide inactivation of tyrosinase by L-DOPA and AH2. The main aim of this work was to compare processes with native and immobilized tyrosinase to identify ...
متن کاملThe hydroxylation of phenylalanine and tyrosine by tyrosine hydroxylase from cultured pheochromocytoma cells.
Pheochromocytoma tyrosine hydroxylase was reported to have unusual catalytic properties, which might be unique to the tumor enzyme (Dix, T. A., Kuhn, D. M., and Benkovic, S. J. (1987) Biochemistry 24, 3354-3361). Two such properties, namely the apparent inability to hydroxylate phenylalanine and an unprecedented reactivity with hydrogen peroxide were investigated further in the present study. T...
متن کاملCatecholamines and the hydroxylation of tyrosine in synaptosomes isolated from rat brain.
Tyrosine hydroxylase activity of synaptosomes isolated from rat brain was examined. A modified tritium-displacement assay was used, which allowed the measurement of tyrosine hydroxylase activity without the addition of either inhibitors of the metabolism of the hydroxylated products or added exogenous cofactor. The enzyme activity was strongly inhibited by the addition of exogenous catecholamin...
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 کاملIsotope effects in mechanistic studies of l-tyrosine halogen derivatives hydroxylation catalyzed by tyrosinase
The kinetic (KIE) and solvent (SIE) isotope effect methods were used to investigate the mechanism of enzymatic hydroxylation of halogenated derivatives of l-tyrosine to l-DOPA catalyzed by the enzyme tyrosinase (EC 1.14.18.1). The values of deuterium KIE and SIE were obtained using the non-competitive method with spectrophotometric measurements. The Lineweaver-Burk plots were used for determina...
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ژورنال
عنوان ژورنال: Journal of Investigative Dermatology
سال: 1979
ISSN: 0022-202X
DOI: 10.1111/1523-1747.ep12551743