In order to obtain information on the correlation between the biosynthesis of proline from glutamate and photosynthesis in green leaves, the effects of various substances on proline formation from 14C-glutamate have been investigated using tobacco leaf disks in the light. Inhibitors of oxygen evolution in photosynthesis, such as CMU, strongly inhibited the proline formation. The inhibition could not be reversed by the addition of reduced NADP, ascorbate plus 2,6-dichlorophenol-indophenol or ATP. Uncouplers or inhibitors of photophosphorylation such as DNP, arsenate, chlorpromazine and octyl guanidine suppressed the formation of proline from glutamate. In old leaves, the addition of ADP or ATP markedly accelerated proline formation, while neither of these compounds was effective in young leaves. It was inferred that the reduction of glutamate to δ1-pyrroline-5-carboxylate in green leaves is closely associated with noncyclic photophosphorylation.
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Noguchi et al. (1968) studied this question.