Light-induced D1 protein degradation is catalyzed by a serine-type protease.

Light-induced degradation of the D1 protein in isolated spinach photosystem II core preparations was studied after addition of various protease inhibitors. The degradation was selectively inhibited by several serine protease inhibitors in particular diisopropylfluorophosphate. The results demonstrate that the D1 protein is degraded by a serine-type of proteolytic activity that is an integral part of photosystem II.