[Codases: fifty years after].

Aminoacyl-tRNA synthetases (codases) catalyze aminoacylation of a particular tRNA with the corresponding amino acid at the first step of protein biosynthesis. The review considers universal structure-functional characteristics of the largest family of enzymes partitioned into two classes. Modes of tRNA binding and recognition, and additional editing activity, which are responsible for the fidelity of aminoacyl-tRNA synthesis, are discussed. The aaRSs catalytic cores are highly relevant to the ancient metabolic reactions, namely, amino acids and cofactors biosynthesis. Thus, the biosynthetic machinery for producing amino acids had a profound effect on almost every aspect of aminoacylation reaction. The review also deals with secondary functions of synthetases in various processes of cell metabolism. Certain of these functions have to do with complex pathophysiological mechanisms involved in disease production. Their investigation may help to develop new diagnostic techniques and therapies.