Photoactive pigment-enzyme complexes of chlorophyll precursor in plant leaves.
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This review summarizes contemporary data on structure and function of photoactive pigment--enzyme complexes of the chlorophyll precursor that undergoes photochemical transformation to chlorophyllide. The properties and functions of the complex and its principal components are considered including the pigment (protochlorophyllide), the hydrogen donor (NADPH), and the photoenzyme protochlorophyllide oxidoreductase (POR) that catalyzes the photochemical production of chlorophyllide. Chemical variants of the chlorophyll precursor are described (protochlorophyllide, protochlorophyll, and their mono- and divinyl forms). The nature and photochemical activity of spectrally distinct native protochlorophyllide forms are discussed. Data are presented on structural organization of the photoenzyme POR, its substrate specificity, localization in etioplasts, and heterogeneity. The significance of different POR forms (PORA, PORB, and PORC) in adaptation of chlorophyll biosynthesis to various illumination conditions is considered. Attention is paid to structural and functional interactions of three main constituents of the photoactive complex and to possible existence of additional components associated with the pigment-enzyme complex. Historical aspects of the problem and the prospects of further investigations are outlined. (+info)
PIF1 directly and indirectly regulates chlorophyll biosynthesis to optimize the greening process in Arabidopsis.
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Monogalactosyldiacylglycerol deficiency in Arabidopsis affects pigment composition in the prolamellar body and impairs thylakoid membrane energization and photoprotection in leaves.
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Chloroplast biogenesis. Detection of monovinyl protochlorophyll(ide) b in plants.
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The occurrence of protochlorophyllide b and protochlorophyllide b phytyl ester in green plants is described. The chemical structure of protochlorophyllide b phytyl ester was established by proton nuclear magnetic resonance, fast atom bombardment mass spectroscopic analysis, and chemical derivatization coupled to electronic spectroscopic analysis. The macrocycles of protochlorophyll(ide) b are identical to those of conventional protochlorophyll(ide) except for the presence of a formyl group instead of a methyl group at position 3 of the macrocycles. They differ from chlorophyll(ide) b by the presence of an oxidized double bond at positions 7 and 8 of the macrocycles. The trivial name protochlorophyll(ide) b is proposed to differentiate these two tetrapyrroles from conventional protochlorophyll(ide), which in turn will be referred to as protochlorophyll(ide) a. Protochlorophyll(ide) b appears to be widely distributed in green plants. Its molar extinction coefficients in 80% acetone and diethyl ether are reported. The impact of this discovery on the heterogeneity of the chlorophyll a and b biosynthetic pathways is discussed. (+info)