کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
9882099 1536538 2005 10 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Enzymatic characterization of human mitochondrial C1-tetrahydrofolate synthase
موضوعات مرتبط
علوم زیستی و بیوفناوری بیوشیمی، ژنتیک و زیست شناسی مولکولی زیست شیمی
پیش نمایش صفحه اول مقاله
Enzymatic characterization of human mitochondrial C1-tetrahydrofolate synthase
چکیده انگلیسی
A human mitochondrial isozyme of C1-tetrahydrofolate (THF) synthase was previously identified by its similarity to the human cytoplasmic C1-THF synthase. All C1-THF synthases characterized to date, from yeast to human, are trifunctional, containing the activities of 5,10-methylene-THF dehydrogenase, 5,10-methenyl-THF cyclohydrolase, and 10-formyl-THF synthetase. Here we report on the enzymatic characterization of the recombinant human mitochondrial isozyme. Enzyme assays of purified human mitochondrial C1-THF synthase protein revealed only the presence of 10-formyl-THF synthetase activity. Gel filtration and crosslinking studies indicated that human mitochondrial C1-THF synthase exists as a homodimer in solution. Steady-state kinetic characterization of the 10-formyl-THF synthetase activity was performed using (6R,S)-H4-PteGlu1, (6R,S)-H4-PteGlu3, and (6R,S)-H4-PteGlu5 substrates. The (6R,S)-H4-PteGlunKm dropped from greater than 500 μM for the monoglutamate to 15 μM and 3.6 μM for the tri- and pentaglutamates, respectively. The Km values for formate and ATP also are lowered when THF polyglutamates are used. The formate Km dropped 79-fold and the ATP Km dropped more than 5-fold when (6R,S)-H4-PteGlu5 was used as the substrate in place of (6R,S)-H4-PteGlu1.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Archives of Biochemistry and Biophysics - Volume 442, Issue 2, 15 October 2005, Pages 196-205
نویسندگان
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