A new inhibitor protein from rat uterus against yeast proteinase B

An inhibitor of yeast proteinase B has been enriched from uterine smooth muscle (myometrium) of the rat. This inhibitor behaves like a glycoprotein and has a molecular weight of 90 000. It activity can be clearly distinguished from the proteinase inhibitory activity of serum. Proteinase B inhibitory activity has also been demonstrated in liver, lung, heart, skeletal muscle, spleen and brain and these activities, too, are clearly distinguishable from the serum inhibitory activity. The activity in rat uterus decreases during the postpartal period.