 Furthermore, the gamma subunit significantly accelerates the rate of oxaloacetate decarboxylation in the alpha subunit, and this correlates with the coordination of a Zn2+ metal ion by several residues at the hydrophilic C-terminus.The alpha subunit, which is ~65kDa, is a biotinylated peripheral membrane protein on the cytosolic side of the membrane.Within the alpha subunit is the carboxyl transferase (CT) domain, oxaloacetate decarboxylase gamma association domain, and biotin carboxyl carrier domain.