Valine 

Valine is one of the three branched-chain amino acids (BCAAs) along with leucine and isoleucine. Valine does not have much use when taken alone and is best used when paired with the other BCAAs (1). 

1.Lynch CJ, et al. Regulation of amino acid-sensitive TOR signaling by leucine analogues in adipocytes. J Cell Biochem. (2000)