Studies in Protein Metabolism

There is no doubt that animals can synthesize certain amino acids, the ultimate source of the nitrogen being that of the food protein. This process probably occurs under normal conditions, as the average composition of food proteins is never the same as that of the body proteins into which they have to be converted. According to the generally accepted theory, amino acid synthesis in the animal follows the scheme by which ammonia reacts with cu-keto acids to form imino acids which are reduced to amino acids. Knoop and Oesterlin (1) have followed this reaction in in vitro experiments.