کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
1393651 | 983966 | 2014 | 9 صفحه PDF | دانلود رایگان |
• We have deciphered the reaction pathway of a cofactor-independent dioxygenase
• The mechanism of cofactor-independent O2 activation was elucidated
• Base-catalyzed substrate activation is followed by substrate-assisted O2 activation
• The mechanism likely applies for most, if not all, cofactor-independent oxygenases
SummaryIn contrast to the majority of O2-activating enzymes, which depend on an organic cofactor or a metal ion for catalysis, a particular group of structurally unrelated oxygenases is functional without any cofactor. In this study, we characterized the mechanism of O2 activation in the reaction pathway of a cofactor-independent dioxygenase with an α/β-hydrolase fold, which catalyzes the oxygenolytic cleavage of 2-alkyl-3-hydroxy-4(1H)-quinolones. Chemical analysis and electron paramagnetic resonance spectroscopic data revealed that O2 activation in the enzyme’s active site is substrate-assisted, relying on single electron transfer from the bound substrate anion to O2 to form a radical pair, which recombines to a C2-peroxide intermediate. Thus, an oxygenase can function without a cofactor, if the organic substrate itself, after activation to a (carb)anion by an active-site base, is intrinsically reactive toward molecular oxygen.
Journal: - Volume 21, Issue 2, 20 February 2014, Pages 217–225