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Fig. 2 | SpringerPlus

Fig. 2

From: Simultaneous quantification of salivary 3-hydroxybutyrate, 3-hydroxyisobutyrate, 3-hydroxy-3-methylbutyrate, and 2-hydroxybutyrate as possible markers of amino acid and fatty acid catabolic pathways by LC–ESI–MS/MS

Fig. 2

Productive pathways of 3HIB from VAL and 3HMB from LEU in BCAA metabolism. BCAAs are metabolized in the mitochondrion and the first two steps are catalyzed by common enzymes; first, BCAAs are deaminated to the respective BCKA by BCAT, and then the BCKAs are converted to the respective CoA-derivatives by the BCKDH complex, which is the rate-limiting enzyme in BCAA catabolism. The respective CoA derivatives are finally metabolized to Ac-CoA and/or Suc-CoA. 3HIB is an intermediate of VAL catabolism that is released from 3HIB-CoA by HIBCH in the mitochondrion. The small molecule 3HIB leaks into extracellular fluid. 3HMB is synthesized from KIC by KICDO in the cytoplasm as a BCKA derived from LEU. 3HMB is also detectable in extracellular fluid. 3HIB 3-hydroxyisobutyrate, 3HIB-CoA 3-hydroxyisobutyryl-CoA, α-Kg α-ketoglutaric acid, Ac-CoA acetyl-CoA, BCAA branched-chain amino acid, BCAT branched-chain aminotransferase, BCKA branched-chain α-keto acid, BCKDH complex BCKA dehydrogenase complex, GLU glutamate, KIC α-ketoisocaproic acid, KICDO KIC dioxygenase, KMV α-keto-β-methylvaleric acid, KIV α-ketoisovaleric acid, HIBCH 3HIB-CoA hydrolase, IB-CoA isobutyryl-CoA, ILE isoleucine, Inner m. mitochondria inner membrane, IV-CoA isovaleryl-CoA, LEU leucine, MB-CoA α-methylbutyryl-CoA, MC-CoA methacrylyl-CoA, MMS methylmalonate semialdehyde, Outer m. mitochondrial outer membrane, Plasma m. plasma membrane, PP-CoA propionyl-CoA, Suc-CoA succinyl-CoA, VAL valine

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