Mitochondrial branched-chain-amino-acid aminotransferase (BCAT2) catalyzes the reversible reactions of leucine, isoleucine, or valine with alpha-ketoglutarate (2-oxoglutarate) to form alpha-ketoisocaproate, alpha-keto-beta-methylvalerate, or a-ketoisovalerate, respectively, and glutamate (Bledsoe et al. 1997). The active enzyme is a homodimer (Yennawar et al. 2001, 2002). In the body, this enzyme is widely expressed but is especially abundant in muscle tissue.