Off-pathway, oxygen-dependent thiamine radical in the Krebs cycle.

ABSTRACT: The catalytic cofactor thiamine diphosphate is found in many enzymes of central metabolism and is essential in all extant forms of life. We demonstrate the presence of an oxygen-dependent free radical in the thiamine diphosphate-dependent Escherichia coli 2-oxoglutarate dehydrogenase, which is a key component of the tricarboxylic acid (Krebs) cycle. The radical was sufficiently long-lived to be trapped by freezing in liquid nitrogen, and its electronic structure was investigated by electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR). Taken together, the spectroscopic results revealed a delocalized pi radical on the enamine-thiazolium intermediate within the enzyme active site. The radical is generated as an intermediate during substrate turnover by a side re

SUBMITTER: Frank RA 

PROVIDER: S-EPMC7610923 | biostudies-literature | 2008 Feb

REPOSITORIES: biostudies-literature