کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
1178019 962658 2011 10 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Pyridoxal-5′-phosphate as the catalyst for radical isomerization in reactions of PLP-dependent aminomutases
موضوعات مرتبط
مهندسی و علوم پایه شیمی شیمی آنالیزی یا شیمی تجزیه
پیش نمایش صفحه اول مقاله
Pyridoxal-5′-phosphate as the catalyst for radical isomerization in reactions of PLP-dependent aminomutases
چکیده انگلیسی

PLP catalyzes the 1,2 shifts of amino groups in free radical-intermediates at the active sites of amino acid aminomutases. Free radical forms of the substrates are created upon H atom abstractions carried out by the 5′-deoxyadenosyl radical. In most of these enzymes, the 5′-deoxyadenosyl radical is generated by an iron–sulfur cluster-mediated reductive cleavage of S-adenosyl-(S)-methionine. However, in lysine 5,6-aminomutase and ornithine 4,5-aminomutase, the radical is generated by homolytic cleavage of the cobalt–carbon bond of adenosylcobalamin. The imine linkages in the initial radical forms of the external aldimines undergo radical addition to form azacyclopropylcarbinyl radicals as central intermediates in the catalytic cycles. In the case of lysine 2,3-aminomutase, the multistep catalytic mechanism is corroborated by direct spectroscopic observation and characterization of a product radical trapped during steady-state turnover. Analogues of the substrate-related radical having substituents adjacent to the radical center to stabilize the unpaired electron are also observed and characterized spectroscopically. A functional allylic analogue of the 5′-deoxyadenosyl radical is observed spectroscopically. A high-resolution crystal structure fully supports the mechanistic proposals. Evidence for a similar free radical mediated amino group transfer in the adenosylcobalamin-dependent lysine 5,6-aminomutase is provided by spectroscopic detection and characterization of radicals generated from the 4-thia analogues of the lysine substrates. This article is part of a Special Issue entitled: Pyridoxal Phospate Enzymology.

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ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics - Volume 1814, Issue 11, November 2011, Pages 1548–1557
نویسندگان
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