Carnitine Biosynthesis /3-HYDROXYLATION OF TRIMETHYLLYSINE BY AN a-KETOGLUTARATE-DEPENDENT MITOCHONDRIAL DIOXYGENASE*
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چکیده
Rat liver mitochondria were found to hydroxylate E-Ntrimethyl+lysine to produce P-hydroxy-c-N-trimethyl-L-lysine, an intermediate in carnitine biosynthesis. The hydroxylating system requires a-ketoglutarate, Fez+, and ascorbate, but does not require NADPH nor NADH. No activity was found in the microsomal or soluble fractions of liver extracts. The hydroxylated a-amino acid was isolated and characterized by column chromatography using Dowex 50H+ and Chelex 100~CW+ resins and by high voltage paper electrophoresis. The enzymatically produced P-hydroxy-eN-trimethyl+lysine was shown to be periodate-sensitive and one periodation product was characterized as y-butyrobetaine aldehyde. The hydroxylated product was acted upon by crystalline serine transhydroxymethylase (EC 2.1.2.1) to yield y-butyrobetaine aldehyde and glycine. Conversion of about 40% of the l -N-trimethyl+lysine to phydroxy-•-N-trimethyl+lysine was accomplished by this system with little or no further metabolism.
منابع مشابه
Substrate scope for trimethyllysine hydroxylase catalysis.
Trimethyllysine hydroxylase (TMLH) is a non-haem Fe(ii) and 2-oxoglutarate dependent oxygenase that catalyses the C-3 hydroxylation of an unactivated C-H bond in l-trimethyllysine in the first step of carnitine biosynthesis. The examination of trimethyllysine analogues as substrates for human TMLH reveals that the enzyme does hydroxylate substrates other than natural l-trimethyllysine.
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Trimethyllysine hydroxylase (TMLH) catalyses C-3 hydroxylation of Nε-trimethyllysine in the first step of carnitine biosynthesis in humans. Studies on TMLH have been hampered by the lack of established chemical methods. We report that an Nε-trimethyllysine analogue that contains the fluoromethyl group can be used as a 1H and 19F NMR probe for studies on TMLH catalysis.
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metabolite essential for the transport of long-chain fatty acids from the cytosol into the mitochondrial matrix and is an important player in energy production via b-oxidation. Therefore, carnitine depletion causes a failure of ATP production and an accumulation of triglycerides in tissues such as the liver, skeletal muscle and heart. Animal tissues contain relatively large amounts of carnitine...
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γ-Butyrobetaine hydroxylase (BBOX) is a 2-oxoglutarate dependent oxygenase that catalyzes the final hydroxylation step in the biosynthesis of carnitine. BBOX was shown to catalyze the oxidative desymmetrization of achiral N,N-dialkyl piperidine-4-carboxylates to give products with two or three stereogenic centers.
متن کاملHuman carnitine biosynthesis proceeds via (2S,3S)-3-hydroxy-N ε-trimethyllysine† †Electronic supplementary information (ESI) available: Synthesis procedures, assay conditions, NMR assignments and spectra, and MS analyses. See DOI: 10.1039/c6cc08381a Click here for additional data file.
Nε-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-Nε-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-Nε-trimethyllysine.
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