Abstract
The biosynthesis of 2-oxo-3-methylvalerate in Chlorobium vibrioforme was investigated by 13C nuclear magnetic resonance spectroscopy of the oxoacid formed from 13C-labeled acetate by washed suspensions. The threonine pathway could be excluded, and the results are in accord with a mechanism for the formation of 2-oxobutyrate from acetyl coenzyme A and pyruvate via citramalate.