کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
1178005 962658 2011 7 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
The PLP cofactor: Lessons from studies on model reactions
موضوعات مرتبط
مهندسی و علوم پایه شیمی شیمی آنالیزی یا شیمی تجزیه
پیش نمایش صفحه اول مقاله
The PLP cofactor: Lessons from studies on model reactions
چکیده انگلیسی

Experimental probes of the acidity of weak carbon acids have been developed and used to determine the carbon acid pKas of glycine, glycine derivatives and iminium ion adducts of glycine to the carbonyl group, including 5′-deoxypyridoxal (DPL). The high reactivity of the DPL-stabilized glycyl carbanion towards nucleophilic addition to both DPL and the glycine-DPL iminium ion favors the formation of Claisen condensation products at enzyme active sites. The formation of the iminium ion between glycine and DPL is accompanied by a 12-unit decrease in the pKa of 29 for glycine. The complicated effects of formation of glycine iminium ions to DPL and other aromatic and aliphatic aldehydes and ketones on carbon acid pKa are discussed. These data provide insight into the contribution of the individual pyridine ring substituents to the catalytic efficiency of DPL. It is suggested that the 5′-phosphodianion group of PLP may play an important role in enzymatic catalysis of carbon deprotonation by providing up to 12 kcal/mol of binding energy that is utilized to stabilize the transition state for the enzymatic reaction. This article is part of a Special Issue entitled: Pyridoxal Phospate Enzymology.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics - Volume 1814, Issue 11, November 2011, Pages 1419–1425
نویسندگان
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