Stereochemistry of Valine Biosynthesis

Abstract
When .alpha.-aceto[1,3,5-13C3]lactate (2-hydroxy-2-methyl-3-oxo[1,3,5-13C3]butanoate) was incubated with a cell-free system prepared from Salmonella typhimurium, the valine produced was labeled in the C-4 pro-S position. This result proves that during the tertiary ketol rearrangement catalyzed by the reductoisomerase of the isoleucine-valine pathway, the methyl group transfer is to the re face of the trigonal centre at C-3 of .alpha.-acetolactate.