Seed proteases and protease inhibitors

Abstract

This review, which unavoidably has to be of a highly selective nature, covers the literature through December, 1967, and is concerned with two classes of proteins which are involved in the metabolism of seeds: proteases and protease inhibitors. During germination, proteases degrade protein reserves of seeds with an attendant release of peptides, free amino acids, and amides. The bulk of these degradation products is utilized by the developing embryo for the synthesis of new protein. Seed proteases are often associated with inhibitors, the function of which has not been established. It has been suggested that inhibitors play a decisive part in the regulation of protein metabolism (1), and indeed Honovar & Sohonie (2) observed a relatively high concentration of inhibitor in young and growing leaf tissue as compared to older tissue. Recently Ryan & Huisman (3) showed that the Chymotrypsin Inhibitor I of potato is synthesized in leaves and translocated to the meristematic parts, where rapid protein synthesis occurs. Inhibition of proteolysis would also be desirable in immature seed or other reproductive storage organs where a similar situation exists with regard to protein synthesis.