Methylcrotonyl-CoA explained

3-Methylcrotonyl-CoA (β-Methylcrotonyl-CoA or MC-CoA) is an intermediate in the metabolism of leucine.^[1]

It is found in mitochondria, where it is formed from isovaleryl-coenzyme A by isovaleryl coenzyme A dehydrogenase. It then reacts with CO₂ to yield 3-Methylcrotonyl-CoA carboxylase. ^[2]

See also

• Methylcrotonyl-CoA carboxylase

Notes and References

1. Zanchi NE, Gerlinger-Romero F, Guimarães-Ferreira L, de Siqueira Filho MA, Felitti V, Lira FS, Seelaender M, Lancha AH . 6 . HMB supplementation: clinical and athletic performance-related effects and mechanisms of action . Amino Acids . 40 . 4 . 1015–1025 . April 2011 . 20607321 . 10.1007/s00726-010-0678-0 . 11120110 . HMB is a metabolite of the amino acid leucine (Van Koverin and Nissen 1992), an essential amino acid. The first step in HMB metabolism is the reversible transamination of leucine to [α-KIC] that occurs mainly extrahepatically (Block and Buse 1990). Following this enzymatic reaction, [α-KIC] may follow one of two pathways. In the first, HMB is produced from [α-KIC] by the cytosolic enzyme KIC dioxygenase (Sabourin and Bieber 1983). The cytosolic dioxygenase has been characterized extensively and differs from the mitochondrial form in that the dioxygenase enzyme is a cytosolic enzyme, whereas the dehydrogenase enzyme is found exclusively in the mitochondrion (Sabourin and Bieber 1981, 1983). Importantly, this route of HMB formation is direct and completely dependent of liver KIC dioxygenase. Following this pathway, HMB in the cytosol is first converted to cytosolic β-hydroxy-β-methylglutaryl-CoA (HMG-CoA), which can then be directed for cholesterol synthesis (Rudney 1957) (Fig. 1). In fact, numerous biochemical studies have shown that HMB is a precursor of cholesterol (Zabin and Bloch 1951; Nissen et al. 2000). .
2. Grünert SC, Stucki M, Morscher RJ, Suormala T, Bürer C, Burda P, Christensen E, Ficicioglu C, Herwig J, Kölker S, Möslinger D, Pasquini E, Santer R, Schwab KO, Wilcken B, Fowler B, Yue WW, Baumgartner MR . 6 . 3-methylcrotonyl-CoA carboxylase deficiency: clinical, biochemical, enzymatic and molecular studies in 88 individuals . Orphanet Journal of Rare Diseases . 7 . 1 . 31 . May 2012 . 22642865 . 3495011 . 10.1186/1750-1172-7-31 . free .