Pyridoxal-5′-phosphate as the catalyst for radical isomerization in reactions of PLP-dependent aminomutases

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