PROTEOLYTIC ACTIVITIES IN THE DEVELOPING SEEDS OF X HAYNALDOTICUM SARDOUM

Aminopeptidase, carboxypeptidase and proteinase activities were measured in endosperms from unripe and ripe seeds of x Haynaldoticum sardoum. Aminopeptidase and proteinase activities were high during the early maturation stages and then decreased. In contrast, carboxypeptidase activity increased with maturation. Localization studies demonstrated that aminopeptidase and carboxypeptidase activities were present in the three tissues examined (pericarp, green layer plus aleurone, and starchy endosperm). Proteinase activity against gliadin was located in the pericarp and in the green layer plus aleurone, but was absent in the starchy endosperm. The presence of proteolytic activities in the outer kernel layers might be correlated to the hydrolysis of transitory protein reserves during the senescence of the seed coats. Aminopeptidase and carboxypeptidase activities located in the starchy endosperm could participate in the breakdown of protein reserves during the early phases of seed germination.