Stereochemistry of the decarboxylation of α-acetolactate (2-hydroxy-2-methyl-3-oxobutanoate) by the acetolactate decarboxylase of Klebsiella aerogenes

[3-14C]-α-Acetolactate ([3-14C]-2-hydroxy-2-methyl-3-oxobutanoate) was synthesised and subjected to enzymatic decarboxylation by the acetolactate decarboxylase from Klebsiella pneumoniae. Degradation of the acetoin produced showed that the radioactivity was largely confined to the acetyl component. Together with previous results, this proves that during decarboxylation the carboxy group of α-acetolactate is replaced regiospecifically by hydrogen and that this process takes place with overall inversion of configuration.