کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
10582861 981129 2005 8 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
The effective molarity of the substrate phosphoryl group in the transition state for yeast OMP decarboxylase
موضوعات مرتبط
مهندسی و علوم پایه شیمی شیمی آلی
پیش نمایش صفحه اول مقاله
The effective molarity of the substrate phosphoryl group in the transition state for yeast OMP decarboxylase
چکیده انگلیسی
The second order rate constant (kcat/Km) for decarboxylation of orotidine by yeast OMP decarboxylase (ODCase), measured by trapping 14CO2 released during the reaction, is 2 × 10−4 M−1 s−1. This very low activity may be compared with a value of 3 × 107 M−1 s−1 for the action of yeast OMP decarboxylase on the normal substrate OMP. Both activities are strongly inhibited by 6-hydroxy UMP (BMP), and abrogated by mutation of Asp-96 to alanine. These results, in conjunction with the binding affinity of inorganic phosphate as a competitive inhibitor (Ki = 7 × 10−4 M), imply an effective concentration of 1.1 × 109 M for the substrate phosphoryl group in stabilizing the transition state for enzymatic decarboxylation of OMP. The observed difference in rate (1.5 × 1011-fold) is the largest effect of a simple substituent that appears to have been reported for an enzyme reaction.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Bioorganic Chemistry - Volume 33, Issue 1, February 2005, Pages 45-52
نویسندگان
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