Studies on nitrogen metabolism in tobacco plants IX. Effect of various compounds on proline biosynthesis in the green leaves

In order to obtain information on the correlation between thebiosynthesis of proline from glutamate and photosynthesis ingreen leaves, the effects of various substances on proline formationfrom ¹⁴C-glutamate have been investigated using tobacco leafdisks in the light. Inhibitors of oxygen evolution in photosynthesis,such as CMU, strongly inhibited the proline formation. The inhibitioncould not be reversed by the addition of reduced NADP, ascorbateplus 2,6-dichlorophenol-indophenol or ATP. Uncouplers or inhibitorsof photophosphorylation such as DNP, arsenate, chlorpromazineand octyl guanidine suppressed the formation of proline fromglutamate. In old leaves, the addition of ADP or ATP markedlyaccelerated proline formation, while neither of these compoundswas effective in young leaves. It was inferred that the reductionof glutamate to ¹-pyrroline-5-carboxylate in green leaves isclosely associated with noncyclic photophosphorylation. (Received August 17, 1967; )