I & J are Isoleucine

Isoleucine is I and J. The amino acid Isoleucine is most commonly represented by the letter I and can also be used to represent the letter J. As an essential amino acid, isoleucine is not synthesized in animals, hence it must be ingested, usually as a component of proteins. In plants and microorganisms, it is synthesized via several steps, starting from pyruvic acid and alpha-ketoglutarate.