A. Clark Griffin

Role of Hormones in the Biosynthesis of Polypeptides

The cytoplasmic-polysomal system accounts for a high proportion of all proteins, including many of the hormones, that are synthesized in mammalian cells. However, protein or polypeptide synthesis does occur in the mitochondria and the nucleus. Mention should also be made of the fact that other mechanisms for the biosynthesis of peptides exist, such as the nucleic acid-independent formation of gramicidin S from the interaction of an enzyme-phenylalanine complex with a polyenzyme system charged with the four addition amino acids (Kleinkauf et al., 1969). Most studied of these is the cytoplasmic-polysomal system, and a rather universal mechanistic pattern is beginning to emerge. In-vitro systems for incorporating amino acids now have been isolated from a large number of mammalian tissues including rabbit reticulocytes, liver, tumor cells, pancreas, brain, human tissues, etc. From these investigations, it is quite evident that the basic mechanism of protein biosynthesis is similar in all mammalian cells. In fact, the elaborate studies in vitro involving components isolated from plant and from microbial sources suggest that this basic mechanism operates in all living cells.