PHOTOSYNTHETICA

Photosynthetica 1997, 33(14):569-581 | DOI: 10.1023/A:1006873815045

Chloroplast biogenesis 76. Regulation of 4-vinyl reduction during conversion of divinyl Mg-protoporphyrin IX to monovinyl protochlorophyllide a is controlled by plastid membrane and stromal factors

J.S. Kim^1,2, V. Kolossov¹, C.A. Rebeiz^1,*

¹ Laboratory of Plant Pigment Biochemistry and Photobiology, University of Illinois, Urbana, U.S.A

² Screening Research Division, Korea Research Institute of Chemical Technology, Taejeon 305-606, Korea

Most of the chlorophyll (Chl) a of green plants is formed via two biosynthetic routes, namely the carboxylic divinyl and monovinyl chlorophyll biosynthetic routes. These two routes are linked by (4-vinyl) reductases that convert divinyl tetrapyrroles to monovinyl tetrapyrroles by reduction of the vinyl group at position four of the macrocycle to ethyl. The activities of these two routes are very sensitive to cell disruption. For example in barley leaves, cell disruption, a mandatory step during plastid isolation, results in partial inactivation of the carboxylic divinyl route. Investigations with subplastidic fractions revealed that the carboxylic divinyl and monovinyl biosynthetic routes were regulated by a delicate interaction that involved plastid membranes, stroma, and reduced pyridine nucleotides. While the monovinyl biosynthetic route was very active in isolated plastid membranes, activation of the divinyl biosynthetic route required the joint presence of plastid membranes and stroma. Contrary to expectation, activity of the carboxylic divinyl biosynthetic route was greatly enhanced by addition of NADPH to the lysing buffer used during plastid membranes and stroma preparation. NADPH in cooperation with the plastid stroma may play an important regulatory role during the biosynthesis of divinyl and monovinyl protochlorophyllide a.

Additional key words: Hordeum vulgare; NADPH

Prepublished online: January 1, 1998; Published: December 1, 1997  Show citation