Site of Synthesis of NADPH: Protochlorophyllide Oxidoreductase in Rye (Secale cereale).

The site of synthesis of the plastid membrane-located enzyme, protochlorophyllide reductase, has been determined. Plastid ribosome-deficient and normal rye (Secale cereale L., cv Rheidol) plants were grown in darkness at 33 degrees C and 22 degrees C, respectively. Extracts from these plants were analyzed for the levels of different ribosomal RNAs and cytochrome f and the activity of a number of enzymes with well-established sites of synthesis. The results confirmed that the higher temperature had induced a specific inhibition of protein synthesis in the plastids. The activity and level of protochlorophyllide reductase was unaffected by growth at the higher temperature, suggesting it to be a cytoplasmically synthesized enzyme.