L-Threonine

L-Threonine is an essential amino acid, that is, humans must obtain it from foods because their bodies cannot synthesize it. Foods that contain high amounts of protein, such as meats, fish, eggs, and dairy products, are good sources of L-threonine.

L-Threonine, abbreviated Thr, is the last common amino acid to be discovered. Although biochemist William C. Rose and colleagues at the University of Illinois (Urbana–Champaign) are usually credited with discovering Thr in 1936, biochemist Samuel B. Schryver and botanist H. W. Buston at Imperial College London reported isolating it from oat protein in 1926.

Threonine has two chiral centers and therefore four possible stereoisomers. The isomers other than Thr (D-, L-allo-, and D-allo-threonine) are rare in nature and have no value, nutritional or otherwise.

These days, most Thr is synthesized rather than being obtained from natural proteins. But this past April, Evonik Industries (Essen, Germany) feeling competitive pressure, closed its L-threonine plant in Kaba, Hungary, causing ≈120 people to lose their jobs.