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N6-Trimethyl-lysine metabolism. 3-Hydroxy-N6-trimethyl-lysine and carnitine biosynthesis.

ABSTRACT: Rats injected with N6-[Me-3H]trimethyl-lysine excrete in the urine five radioactively labelled metabolites. Two of these identified metabolites are carnitine and 4-trimethylammoniobutyrate. A third metabolite, identified as 5-trimethylammoniopentanoate, is not an intermediate in the biosynthesis of carnitine; the fourth and major metabolite, N2-acetyl-N6-trimethyl-lysine, is not a precursor of carnitine. The remaining metabolite (3-hydroxy-N6-trimethyl-lysine) is converted into trimethylammoniobutyrate and carnitine by rat liver slices and into trimethylammoniobutyrate by rat kidney slices. In rat liver and kidney-slice experiments, radioactivity from DL-N6-trimethyl-[1-14C]lysine and DL-N6-trimethyl-[2-14C]lysine was incorporated into N2-acetyl-N6-trimethyl-lysine and 3-hydroxy-N6-trimethyl-lysine, but not into trimethylammoniobutyrate or carnitine. A procedure was devised to purify milligram quantities of 3-hydroxy-N6-trimethyl-lysine from the urine of rats injected chronically with N6-trimethyl-lysine (100 mg/kg body wt. per day). The structure of 3-hydroxy-N6-trimethyl-lysine was confirmed chemically and by nuclear-magnetic-resonance spectrometry [Novak, Swift & Hoppel (1980) Biochem. J. 188, 521--527]. The sequence for carnitine biosynthesis in liver is: N6-trimethyl-lysine leads to 3-hydryxy-N6-trimethyl-lysine leads to leads to 4-trimethylammoniobutyrate leads to carnitine.

SUBMITTER: Hoppel CL

PROVIDER: S-EPMC1161895 | biostudies-other | 1980 May

REPOSITORIES: biostudies-other

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Carnitine biosynthesis. Hydroxylation of N6-trimethyl-lysine to 3-hydroxy-N6-trimethyl-lysine.

Project description:Rat kidney homogenates metabolize N6-trimethyl-lysine to N-trimethylammoniobutyrate, but not to carnitine. The first step in this conversion is the hydroxylation of trimethyl-lysine to form 3-hydroxy-N6-trimethyl-lysine. An assay system was developed in which hydroxylation of trimethyl-lysine is linear with respect to both time and homogenate protein concentration. The rate is 5 nmol of 3-hydroxy-N6-trimethyl-lysine formed/min per mg of homogenate protein. The cofactors required are ascorbate, alpha-oxoglutarate, FeSO4, and O2. Catalase and dithiothreitol give a 20% stimulation. Ca2+ produces a 2-fold increase in specific activity and cannot be replaced by Mg2+, Mn2+ or Zn2+. These last three bivalent cations lead to a decreased activity. Subcellular distribution studies demonstrate that trimethyl-lysine hydroxylase activity parallels the distribution profile of succinate dehydrogenase and citrate synthase. Thus trimethyl-lysine hydroxylase has a mitochondrial localization. Distribution of trimethyl-lysine hydroxylase activity between cortex and medulla of kidney if 67 and 33% respectively, similar to mitochondrial distribution.

| S-EPMC1161897 | biostudies-other

N6-Trimethyl-lysine metabolism. Structural identification of the metabolite 3-hydroxy-N6-trimethyl-lysine.

Project description:(1)H and (13)C nuclear-magnetic-resonance spectroscopy and functional-group analysis were used to determine the molecular structure of an isolated metabolite (II(b)) of trimethyl-lysine as 3-hydroxy-N(6)-trimethyl-lysine, an important intermediate in the conversion of trimethyl-lysine into trimethylammoniobutyrate and carnitine [Hoppel, Cox & Novak (1980) Biochem. J.188, 509-519]. Functional-group analysis revealed the presence of a primary amine and reaction of metabolite (II(b)) with periodate yielded 4-N-trimethylammoniobutyrate as a product, showing 2,3-substitution on the molecule and suggesting that the 3-substitution on the molecule may be an alcohol ([unk]CH-OH), amine ([unk]CH[unk]-NH(2)) or carbonyl ([unk]C=O) functional group. (1)H integration ratios, (1)H and (13)C chemical-shift data and (1)H and (13)C signal multiplicities from the sample (II(b)) were used to complete the identification of metabolite (II(b)) as 3-hydroxy-N(6)-trimethyl-lysine. For example, the proton multiplet at delta 4.2p.p.m. and doublet at delta 4.1p.p.m., positions representative of amine or alcohol substitution on methylene carbon atoms, integration ratios of 1:1:2:9:4 and a positive ninhydrin test suggest 3-hydroxy-N(6)-trimethyl-lysine as the molecular structure for metabolite (II(b)). (13)C chemical-shift data obtained from the sample (II(b)) and compared with several model compounds (trimethylammoniohexanoate, trimethyl-lysine and 3-hydroxylysine) resulted in generation of the spectrum of the metabolite and allowed independent identification of metabolite (II(b)) as 3-hydroxy-N(6)-trimethyl-lysine. The (1)H spectrum of erythro- and threo-3-hydroxylysine are presented for comparison, and the (1)H and (13)C n.m.r. spectra of the erythro-isomer support this analysis.

| S-EPMC1161896 | biostudies-other

Biosynthesis of carnitine and 4-N-trimethylaminobutyrate from 6-N-trimethyl-lysine.

Project description:The conversion of 6-N-[Me-(14)C]trimethyl-lysine into carnitine and 4-N-trimethylaminobutyrate (butyrobetaine) was demonstrated in rats kept on a lysine-deficient diet. After the rats were given [(14)C]trimethyl-lysine for 4 days, a total of 17% of the injected label was recovered as carnitine from carcass and urine extracts. Another 8% of the trimethyl-lysine label was converted into 4-N-trimethylaminobutyrate, most of which was recovered from the urine. The conversion of trimethyl-lysine into the above two metabolites supports the pathway of carnitine biosynthesis as lysine+methionine --> 6-N-trimethyl-lysine --> 4-N-trimethylaminobutyrate --> carnitine. In addition, three other metabolites representing 2% of the injected dose were recovered. Only an insignificant portion of the label was recovered as free trimethyl-lysine from the carcass, whereas 22% of the injected label was recovered in the urine. A relatively low specific radioactivity in carnitine was found when 5-N-[Me-(14)C]trimethylaminopentanoate and 6-N-[Me-(14)C]trimethylaminohexanoate were administered to rats in amounts similar to the [(14)C]trimethyl-lysine, suggesting that they were not free intermediates.

| S-EPMC1166060 | biostudies-other

Hepatic synthesis of carnitine from protein-bound trimethyl-lysine. Lysosomal digestion of methyl-lysine-labelled asialo-fetuin.

Project description:The biosynthesis of carnitine in the rat was studied by following the metabolism of two radioactive derivatives of asialo-fetuin. The first contained 14C-labelled methyl groups covalently bound to the 6-N-amino fraction of its lysine residues as 6-N-monomethyl- and dimethyl-lysine. By treating this protein with iodomethane, a second derivative was produced in which the radioactivity was preferentially incorporated as 6-N-[Me-14C]-trimethyl-lysine. These desialylated glycoproteins, like other asialo-proteins, were immediately cleared from the blood by rat liver. Within hepatocyte lysosomes, the 14C-labelled proteins were rapidly hydrolysed, producing free amino acids containing the various 6-N-[Me-14C]methylated lysine residues. The radioactive amino acids crossed the lysosomal membrane and were further metabolized in the cytosol. Carnitine was the major radioactive metabolite detected in extracts of the rat carcass and liver after intravenous injection of 6-N-[Me-14C]trimethyl-lysine-labelled asialo-fetuin. Within 3h, at least 34.6% of the trimethyl-lysine in the administered protein was converted into carnitine. Similarly, an isolated perfused rat liver converted 30% of the added peptide-bound trimethyl-lysine into carnitine within 90 min. On the other hand, in numerous attempts we failed to detect radioactive carnitine in both rat liver and carcass between 20 min and 22 h after injection of 6-N-[Me-14C]-monomethyl- and -dimethyl-lysine-labelled asialo-fetuin. These data provide evidence for a pathway of carnitine biosynthesis that involves trimethyl-lysine as a peptide-bound precursor as proposed by R.A. Cox & C.L. Hoppel [(1973) Biochem. J. 136, 1083-1090] and V. Tanphaichitr & H.P. Broquist [(1973) J. Biol. Chem. 248, 2176-2181]. The findings also show that rat liver can synthesize carnitine without the aid of other tissues, but cannot convert free partially methylated lysines into trimethyl-lysine.

| S-EPMC1164203 | biostudies-other

Human carnitine biosynthesis proceeds via (2S,3S)-3-hydroxy-N<sup>ε</sup>-trimethyllysine.

Project description: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.

| S-EPMC5644716 | biostudies-literature

Biosynthesis of carnitine and 4-N-trimethylaminobutyrate from lysine.

Project description:The conversion of l-[U-(14)C]lysine into carnitine was demonstrated in normal, choline-deficient and lysine-deficient rats. In other experiments in vivo radioactivity from l-[4,5-(3)H]lysine and dl-[6-(14)C]lysine was incorporated into carnitine; however, radioactivity from dl-[1-(14)C]lysine and dl-[2-(14)C]lysine was not incorporated. Administered l-[Me-(14)C]methionine labelled only the 4-N-methyl groups whereas lysine did not label these groups. Therefore lysine must be incorporated into the main carbon chain of carnitine. The methylation of lysine by a methionine source to form 6-N-trimethyl-lysine is postulated as an intermediate step in the biosynthesis of carnitine. Radioactive 4-N-trimethylaminobutyrate (butyrobetaine) was recovered from the urine of lysine-deficient rats injected with [U-(14)C]lysine. This lysine-derived label was incorporated only into the butyrate carbon chain. The specific radioactivity of the trimethylaminobutyrate was 12 times that of carnitine isolated from the urine or carcasses of the same animals. These data further support the idea that the last step in the formation of carnitine from lysine was the hydroxylation of trimethylaminobutyric acid, and are consistent with the following sequence: lysine+methionine --> 6-N-trimethyl-lysine --> --> 4-N-trimethylaminobutyrate --> carnitine.

| S-EPMC1166059 | biostudies-other

Carnitine Palmitoyltransferase 1A Has a Lysine Succinyltransferase Activity.

Project description:Lysine succinylation was recently identified as a post-translational modification in cells. However, the molecular mechanism underlying lysine succinylation remains unclear. Here, we show that carnitine palmitoyltransferase 1A (CPT1A) has lysine succinyltransferase (LSTase) activity in vivo and in vitro. Using a stable isotope labeling by amino acid in cell culture (SILAC)-based proteomics approach, we found that 101 proteins were more succinylated in cells expressing wild-type (WT) CPT1A compared with vector control cells. One of the most heavily succinylated proteins in this analysis was enolase 1. We found that CPT1A WT succinylated enolase 1 and reduced enolase enzymatic activity in cells and in vitro. Importantly, mutation of CPT1A Gly710 (G710E) selectively inactivated carnitine palmitoyltransferase (CPTase) activity but not the LSTase activity that decreased enolase activity in cells and promoted cell proliferation under glutamine depletion. These findings suggest that CPT1A acts as an LSTase that can regulate enzymatic activity of a substrate protein and metabolism independent of its classical CPTase activity.

| S-EPMC5826573 | biostudies-literature

Trimethyllysine: From Carnitine Biosynthesis to Epigenetics.

Project description:Trimethyllysine is an important post-translationally modified amino acid with functions in the carnitine biosynthesis and regulation of key epigenetic processes. Protein lysine methyltransferases and demethylases dynamically control protein lysine methylation, with each state of methylation changing the biophysical properties of lysine and the subsequent effect on protein function, in particular histone proteins and their central role in epigenetics. Epigenetic reader domain proteins can distinguish between different lysine methylation states and initiate downstream cellular processes upon recognition. Dysregulation of protein methylation is linked to various diseases, including cancer, inflammation, and genetic disorders. In this review, we cover biomolecular studies on the role of trimethyllysine in carnitine biosynthesis, different enzymatic reactions involved in the synthesis and removal of trimethyllysine, trimethyllysine recognition by reader proteins, and the role of trimethyllysine on the nucleosome assembly.

| S-EPMC7764450 | biostudies-literature

ScCobB2-mediated Lysine Desuccinylation Regulates Protein Biosynthesis and Carbon Metabolism in Streptomyces coelicolor.

Project description:As a recently discovered protein posttranslational modification in eukaryotes, lysine succinylation has attracted increasing interest due to its ability to regulate several critical cellular processes, including catabolism, ?-oxidation, and ketogenesis. Nevertheless, understanding of the regulatory mechanisms is still at an early stage due to the lack of identified specific desuccinylases in microorganisms. Here, in the model soil bacterium Streptomyces coelicolor, we biochemically characterized a sirtuin-like protein ScCobB2 as a divergent desuccinylase. Based on it, we were able to identify a total of 673 unique succinylated sites, of which 470 sites in 317 proteins were quantified by comparing the ?ScCobB2 to the wild-type succinylome via LC-MS/MS analysis. Further analyses of the quantitative succinylome revealed that at least 114 proteins representing two major pathways, protein biosynthesis and carbon metabolism, are obviously hypersuccinylated in ?ScCobB2 cells. We experimentally examined the regulatory roles of ScCobB2 on 13 hypersuccinylated proteins, including glyceraldehyde-3-phosphate dehydrogenase, aconitate hydratase, and several ribosomal proteins, the results of which suggested a high confidence in our quantitative data. This work provided the first discovery of a specific desuccinylase in bacteria and demonstrated it has pivotal regulatory roles in multiple biological processes of S. coelicolor, laying the foundation for future research of succinylation regulation in other microorganisms.

| S-EPMC6773565 | biostudies-literature

Biosynthesis and degradation of saccharopine, an intermediate of lysine metabolism.

Project description:Lysine-2-oxoglutarate reductase was prepared from ox liver and its characteristics were examined. Its activity was totally inhibited in the presence of NH(4)Cl. Under conditions that inhibit saccharopine formation, and in the presence of NADP(+), ox liver mitochondria were found to catalyse the hydrolysis of saccharopine to lysine and alpha-oxoglutarate. The enzyme involved was named saccharopine oxidoreductase. It was partially purified and separated from lysine-oxoglutarate reductase. Comparison of the properties of these two enzymes showed that saccharopine degradation was stimulated under conditions that inhibit its formation. The effect of pH, various cofactors and stability during incubation confirm that saccharopine biosynthesis from, and degradation to, lysine are catalysed by two distinct enzymes.

| S-EPMC1165957 | biostudies-other

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