Inhibits protein synthesis. Does not cleave supercoiled pBR322 dsDNA. Endohydrolysis of the N-glycosidic bond at one specific adenosine on the 28S rRNA. Detected in developing and mature leaves of adult plants. Levels of PD-L3 and PD-L4 are highest during the spring and summer, fall in autumn and are low during winter. Not detected in young (8-34 month old) plants. PD-L3. PD-L4. PD-L3. 2 forms exist, PD-L3 and PD-L4, that differ in their post-translational modifications. PD-L4 is not glycosylated. Belongs to the ribosome-inactivating protein family. Type 1 RIP subfamily.