Department of Biological Chemistry, University of Michigan Medical School, 1150 W. Medical Center Dr., Ann Arbor, MI 48109-5606, USA.
Arch Biochem Biophys. 2010 Jan 1;493(1):26-36. doi: 10.1016/j.abb.2009.11.028. Epub 2009 Nov 26.
Flavoprotein monooxygenases reduce flavins, speed their reaction with oxygen, and stabilize a C4a-oxygen adduct long enough to use this reactive species to transfer an oxygen atom to a substrate. The flavin-oxygen adduct can be the C4a-peroxide anion, in which case it reacts as a nucleophile. The protonated adduct - the C4a-hydroperoxide - reacts as an electrophile. The elimination of H(2)O(2) competes with substrate oxygenation. This side-reaction is suppressed, preventing the waste of NAD(P)H and the production of toxic H(2)O(2). Several strategies have been uncovered that prevent the deleterious side-reaction while still allowing substrate hydroxylation.
黄素蛋白单加氧酶还原黄素，加速其与氧的反应，并稳定 C4a-氧加合物，使其有足够的时间将一个氧原子转移到底物上。黄素-氧加合物可以是 C4a-过氧阴离子，在这种情况下，它作为亲核试剂反应。质子化的加合物 - C4a-过氢氧化物 - 作为亲电试剂反应。H(2)O(2)的消除与底物氧化竞争。这种副反应被抑制，防止 NAD(P)H 的浪费和有毒 H(2)O(2)的产生。已经发现了几种策略，可以防止有害的副反应，同时仍然允许底物羟化。
