Reversal of relative proteinase F activity and onset of androgen-dependent proteinases in the submandibular gland of postnatal mice

By isoelectric focusing, we separated trypsin-like proteinases of the mouse submandibular gland (ICR strain) into isozymes with pI values of 4.6 (proteinase F), 5.6 (protease D), 5.8 (protease A), 7.1 and 9.9 (P-esterase). During postnatal development, proteinase F appeared earliest (on the 15th day after birth) and increased in both sexes; however, its percentage ratio to total activity decreased markedly with time because of the rapid increase of other proteinases. On the 22nd day of life, proteinases A and D appeared, and the increase of a proteinase with pI-7.1 followed thereafter. P-esterase was the last isozyme to appear, becoming detectable around 29-45 days. After maturation, the activities of protease A plus D, P-esterase, and the isozyme with a pI value of 7.1 were higher in males than in females, whereas the relative level of proteinase F was reversed. We conclude that proteinase F is appreciably different from the other four proteinases in its development pattern as well as in its responsiveness to sexual hormones.