Discovery of L-Threonine

The discovery and scientific naming of L-threonine was a process filled with exploration and research.

In 1935, scientist E. V. McCollum and his colleagues, while studying the nutritional requirements of rats, observed that when a certain unknown amino acid was missing from their diet, the rats exhibited slow growth, weight loss, and skin problems. This led them to hypothesize the existence of a previously unidentified essential amino acid. Subsequently, as they conducted separation and analysis of various protein hydrolysates, they began to notice signs of a new amino acid.

In 1936, W. C. Rose and his team successfully isolated this new amino acid from fibrin hydrolysate. Utilizing advanced chemical separation techniques of the time, including fractional crystallization and ion-exchange chromatography, they conducted multiple rounds of purification and analysis. Eventually, they confirmed the presence of this amino acid and demonstrated that it was an essential amino acid, playing a crucial role in normal growth and development.

Following its discovery, scientists further explored its chemical structure and biological functions. Through chemical synthesis and spectroscopic analysis, they identified its molecular structure and chemical properties. Research revealed that L-threonine plays an important role in protein synthesis, metabolic regulation, and complex interactions with other amino acids.

This newly discovered amino acid was named “threonine”, derived from the Greek word “threos,” meaning “trembling.” The name was inspired by its structural similarity to a known sugar, threose, which exhibits distinctive crystalline changes in certain chemical reactions, giving the impression of "trembling." Due to this structural resemblance, scientists named the new amino acid threonine.

According to organic chemistry’s stereochemical nomenclature, threonine exists in two optical isomers: L-threonine and D-threonine. In nature, L-threonine is the biologically active form that participates in protein synthesis. To clearly distinguish it from D-threonine, the official scientific name explicitly specifies "L-threonine," ensuring clarity regarding its stereochemical configuration.