Results: 5

1.
Figure 1b

Figure 1b. From: ?-Lipoic Acid Induced Elevated S-adenosylhomocysteine and Depleted S-adenosylmethionine.

Two of the major metabolites of lipoic acid are shown; 4, 6-bismethylthiohexanoic acid (BMHA) and 2, 4-bismethylthio-butanoic acid (BMBA). The asterisks demonstrate expected sites of the stable isotope 13C labels after metabolism/catabolism of labeled LA.

Sally P. Stabler, et al. Free Radic Biol Med. ;47(8):1147-1153.
2.
Figure 1a

Figure 1a. From: ?-Lipoic Acid Induced Elevated S-adenosylhomocysteine and Depleted S-adenosylmethionine.

The structures of alpha-lipoic acid (LA) and the reduced form dihydrolipoic acid (DHLA) are shown. The asterisks demonstrate the site of the stable isotope 13C labels in the molecule.

Sally P. Stabler, et al. Free Radic Biol Med. ;47(8):1147-1153.
3.
Figure 3a

Figure 3a. From: ?-Lipoic Acid Induced Elevated S-adenosylhomocysteine and Depleted S-adenosylmethionine.

Gas chromatography/mass spectrometry chromatograms of LA are shown for an assay of 400 uL of control rat serum, as described in Methods. The m-57 ions were monitored. The internal standard ion m/z 267 is shown above and m/z 263 below for the endogenous LA. The calculated result was 0.67 umol/L.

Sally P. Stabler, et al. Free Radic Biol Med. ;47(8):1147-1153.
4.
Figure 3b

Figure 3b. From: ?-Lipoic Acid Induced Elevated S-adenosylhomocysteine and Depleted S-adenosylmethionine.

The gas chromatography/mass spectrometry chromatograms are shown for assay of 20 uL of rat serum 30 minutes after LA 100 mg/kg was injected IP and assayed as described in Fig.4a. The calculated value for serum LA was 20 umol/L.

Sally P. Stabler, et al. Free Radic Biol Med. ;47(8):1147-1153.
5.
Figure 2

Figure 2. From: ?-Lipoic Acid Induced Elevated S-adenosylhomocysteine and Depleted S-adenosylmethionine.

The metabolic pathways of remethylation, transmethylation and transsulfuration are shown (14). Homocysteine can be methylated by either betaine to produce methionine and N, N-dimethylglycine by betaine homocysteine methyltransferase (BHMT) or by 5-methyltetrahydrofolate (5MTHF) by methionine synthase, a reaction dependent on folate and methylcobalamin (MECbl). Methionine is activated to S-adenosylmethionine (SAM) by methionine adenosyltransferase (MAT). SAM is the methyl donor for many transmethylation reactions that produce S-adenosylhomocysteine (SAH). SAH is hydrolysed by S-adenosylhomocysteine hydrolase (SAHH) to homocysteine and adenosine. When methionine is abundant then excess homocysteine is cleared by condensing with serine by cystathionine beta synthase (CBS), a pyridoxal phosphate (PLP)-dependent reaction to form cystathionine and alpha-ketobutyrate. Cystathionine can be cleared by cystathionine gamma lyase (CGL), also PLP-dependent, to form cysteine. Not shown is further metabolism of alpha-ketoglutyrate to alpha -aminobutyric acid. When SAM is in excess, glycine N-methyltransferase (GNMT) methylates glycine to form N-methylglycine.

Sally P. Stabler, et al. Free Radic Biol Med. ;47(8):1147-1153.

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