Mitochondrial branched-chain-amino-acid aminotransferase (BCAT2) catalyzes the reversible reactions of alpha-ketoisocaproate, alpha-keto-beta-methylvalerate, or a-ketoisovalerate with glutamate to form leucine, isoleucine, or valine, respectively, and alpha-ketoglutarate (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.