Methylcrotonoyl-CoA carboxylase subunit alpha, mitochondrial (MCCC1) (MCCC1)

Methylcrotonoyl-CoA carboxylase subunit alpha, mitochondrial (MCCC1) is a biotin-dependent enzyme that catalyzes the fourth step of leucine catabolism, converting 3-methylcrotonyl-CoA to 3-methylglutaconyl-CoA (UniProt, Wikipedia). It functions as the larger subunit of the MCC holoenzyme, a dodecameric complex (α6β6) where MCCC1 provides the biotin-binding and carboxylation domains (Wikipedia, MedlinePlus). Mutations in the MCCC1 gene cause 3-methylcrotonyl-CoA carboxylase deficiency (MCCD), an autosomal recessive metabolic disorder with a highly variable phenotype ranging from neonatal-onset neurological distress to asymptomatic presentation (MedlinePlus, NIH). Beyond its metabolic role, MCCC1 is involved in the innate immune response by interacting with the mitochondrial antiviral-signaling (MAVS) protein to enhance the production of type I interferons and pro-inflammatory cytokines (PubMed, Wikipedia). Genetic studies have also linked MCCC1 variants to an increased risk of Parkinson's disease, suggesting its involvement in neurodegenerative pathways (PubMed, Lancet Neurology). Therapeutic strategies primarily focus on high-dose biotin supplementation to boost enzyme activity and carnitine therapy to manage secondary deficiencies and toxic metabolite accumulation (MedlinePlus, Open Targets).

Other names

MCCAMCCase subunit alpha3-methylcrotonyl-CoA carboxylase 13-methylcrotonyl-CoA carboxylase biotin-containing subunitMethylcrotonoyl-CoA carboxylase alpha chain3-methylcrotonyl-CoA:carbon dioxide ligase subunit alpha

Biotin acts as a necessary cofactor for the carboxylation reaction; therapeutic supplementation aims to maximize residual enzyme activity in patients with deficiency.