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

Area of Science:

• Biochemistry
• Metabolic pathways
• Enzymology

Background:

• Carnitine is essential for fatty acid metabolism in mammals.
• N-epsilon-Trimethyllysine hydroxylase (TMLH) catalyzes the initial step in carnitine biosynthesis.
• The stereochemical outcome of TMLH catalysis was previously undefined.

Purpose of the Study:

• To determine the stereochemistry of the 3-hydroxy-N-epsilon-trimethyllysine product formed by TMLH.
• To elucidate the precise product of the initial enzymatic step in mammalian carnitine biosynthesis.

Main Methods:

• Enzymatic assays using purified N-epsilon-Trimethyllysine hydroxylase.
• Asymmetric synthesis to generate potential product standards.
• Spectroscopic and chromatographic analyses to confirm product identity and stereochemistry.

Main Results:

• The enzymatic product of N-epsilon-Trimethyllysine hydroxylase was identified as (2S,3S)-3-hydroxy-N-epsilon-trimethyllysine.
• Enzymatic and synthetic studies converged to define the specific stereoisomer produced.
• This finding clarifies the stereochemical pathway of carnitine biosynthesis.

Conclusions:

• The stereochemistry of the TMLH-catalyzed reaction has been definitively established.
• The study provides crucial information for understanding carnitine metabolism and related disorders.
• This work resolves a key question in mammalian carnitine biosynthesis.