کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
1952583 1057215 2010 4 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Insight into the reaction mechanism of the Escherichia coli cyclopropane fatty acid synthase: Isotope exchange and kinetic isotope effects
موضوعات مرتبط
علوم زیستی و بیوفناوری بیوشیمی، ژنتیک و زیست شناسی مولکولی زیست شیمی
پیش نمایش صفحه اول مقاله
Insight into the reaction mechanism of the Escherichia coli cyclopropane fatty acid synthase: Isotope exchange and kinetic isotope effects
چکیده انگلیسی

Cyclopropanation of unsaturated lipids is an intriguing enzymatic reaction and a potential therapeutic target in Mycobacterium tuberculosis. Cyclopropane fatty acid synthase from Escherichia coli is the only in vitro model available to date for mechanistic and inhibition studies. While the overall reaction mechanism of this enzymatic process is now well accepted, some mechanistic issues are still debated. Using homogeneous E. coli enzyme we have shown that, contrary to previous report based on in vivo experiments, there is no exchange of the cylopropane methylene protons with the solvent during catalysis, as probed by ultra high resolution mass spectrometry. Using [methyl-14C]-labeled and [methyl-3H3]-S-adenosyl-l-methionine we have measured a significant intermolecular primary tritium kinetic isotope effect (TV/Kapp = 1.8 ± 0.1) consistent with a partially rate determining deprotonation step. We conclude that both chemical steps of this enzymatic cyclopropanation, the methyl addition onto the double bond and the deprotonation step, are rate determining, a common situation in efficient enzymes.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Biochimie - Volume 92, Issue 10, October 2010, Pages 1454–1457
نویسندگان
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