Human carnitine biosynthesis proceeds via (2S,3S)-3-hydroxy-N(ε)-trimethyllysine

N(ε)-Trimethyllysine hydroxylase (TMLH) catalyses the first step in mammalian biosynthesis of carnitine, which plays a crucial role in fatty acid metabolism. The stereochemistry of the 3-hydroxy-N(ε)-trimethyllysine product of TMLH has not been defined. We report enzymatic and asymmetric synthetic studies, which define the product of TMLH catalysis as (2S,3S)-3-hydroxy-N(ε)-trimethyllysine