MCC is a heteromeric biotin-dependent enzyme with a biotin-containing alpha subunit (MCCC1) and a beta subunit; a fungal mccA-null model established the in vivo involvement of MCC in leucine catabolism.

MCC is a heteromeric mitochondrial enzyme composed of biotin-containing alpha subunits and smaller beta subunits; MCCA missense mutations cause loss of function.

The MCCA cDNA encodes a 725-residue protein with a mitochondrial signal peptide, biotin carboxylase, and biotin-carrier domains; MCCase is a mitochondrial biotin enzyme essential for leucine and isovalerate catabolism, abundantly expressed in mitochondria-rich organs.

Both MCC subunits are imported into the mitochondrial matrix by the classical presequence pathway; the MCCalpha cleavage site is Tyr41/Thr42.

Recombinant human MCCC is a heteromultimeric alpha/beta complex (~500-800 kDa) with a 1:1 alpha:beta stoichiometry and measurable carboxylase kinetics (kcat ~4 s-1; Km ATP 45 uM, 3-methylcrotonyl-CoA 74 uM).

Biotin-dependent carboxylases (including MCC) contain biotin carboxylase (BC), carboxyltransferase (CT), and biotin-carboxyl carrier protein components; MCC deficiency is linked to human disease.

MCCC1 is described as a key enzyme in the leucine metabolic pathway; siRNA knockdown of MCCC1 perturbs leucine metabolism and thereby modulates mTORC1 activity and autophagy.

MCCC1 is detected as part of a quantitative high-confidence human mitochondrial proteome.