Methylcrotonoyl-CoA carboxylase subunit beta (MCCB)

Methylcrotonoyl-CoA carboxylase subunit beta is the beta chain of the mitochondrial enzyme methylcrotonoyl-CoA carboxylase, which catalyzes the ATP-dependent biotin-requiring conversion of 3-methylcrotonoyl-CoA to 3-methylglutaconyl-CoA. This reaction represents the fourth step in the breakdown pathway for leucine, an essential branched-chain amino acid. The functional holoenzyme consists of six alpha and six beta subunits encoded by MCCC1 and MCCC2, respectively. Deficiency due to genetic mutations results in an inherited disorder characterized by impaired protein catabolism leading to toxic metabolite accumulation and clinical symptoms such as vomiting, metabolic acidosis, hypoglycemia, and low plasma carnitine levels. The enzyme plays a critical role in energy production from dietary proteins but is not currently considered a direct therapeutic drug target.

Other names

3-methylcrotonyl-CoA carboxylase beta chainMCCC2 (gene symbol)MCCBBeta subunit of methylcrotonoyl-CoA carboxylase