کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
9882213 1536548 2005 10 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Supraphysiological concentrations of 5-aminolevulinic acid dimerize in solution to produce superoxide radical anions via a protonated dihydropyrazine intermediate
موضوعات مرتبط
علوم زیستی و بیوفناوری بیوشیمی، ژنتیک و زیست شناسی مولکولی زیست شیمی
پیش نمایش صفحه اول مقاله
Supraphysiological concentrations of 5-aminolevulinic acid dimerize in solution to produce superoxide radical anions via a protonated dihydropyrazine intermediate
چکیده انگلیسی
5-Aminolevulinic acid (ALA) is the committed biological precursor to porphyrins. At supraphysiological concentrations ALA can dimerize to form 3,6-dihydropyrazine-2,5-dipropanoic acid (DHPY), which transfers electrons to XTT in a reaction that does not require metal ions and is specifically inhibited by superoxide dismutase. The formation of DHPY from ALA follows dimerization kinetics with a pK of 7.8 ± 0.1. At pH 11.2, DHPY is relatively stable, but when the pH is dropped to 6.0 rapid conversion to 2,5-(β-carboxyethyl)pyrazine occurs via an intermediate with an absorption maximum of 370 nm. Formation of this intermediate is pH-dependent with a pK of 6.0 ± 0.1. These data indicate that ALA dimerizes to produce superoxide from a protonated form of DHPY. The significance of these results with respect to the concentrations of ALA used in photodynamic therapy, and the increased incidence of liver cancer in acute intermittent porphyria, is discussed.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Archives of Biochemistry and Biophysics - Volume 437, Issue 2, 15 May 2005, Pages 128-137
نویسندگان
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