Quantitative determination of 2-monovinyl protochlorophyll(ide) b by spectrofluorometry.
Explore the source record for details and available documents.
Cucumis sativus↗
Biomedical subjects
I M Ioannides
Publications and source records attributed to I M Ioannides.
Chlorophyll a biosynthetic heterogeneity.
Chlorophyll a biosynthesis is presently interpreted in terms of two different biochemical pathways. According to one pathway, chlorophyll a is made via a single linear chain of reactions starting with divinylprotoporphyrin IX and ending with monovinylchlorophyll a. The experimental evidence for this pathway is marred by incompletely characterized intermediates that were detected in Chlorella mutants. The second pathway considers chlorophyll a to be made via multiple and parallel biosynthetic routes that result in the formation and accumulation of monovinyl- and divinylchlorophyll a chemical species. Two of these routes, namely the di/monocarboxylic monovinyl and divinyl routes, are responsible for the biosynthesis of most of the chlorophyll a in green plants. The experimental evidence for these two routes consists of: (a) the detection and spectroscopic characterization of intermediates and end products; (b) the demonstration of precursor-product relationships between various intermediates in vivo and in vitro; and (c) the detection of 4-vinylreductases that appear to be mainly responsible for the observed biosynthetic heterogeneity. The biological significance of chlorophyll a biosynthetic heterogeneity is becoming better understood. On the basis of the prevalence of the di/monocarboxylic monovinyl-and divinylchlorophyll a biosynthetic routes, green plants have been classified into three different greening groups. It now appears that the major chlorophylls in the euphotic zone of tropical waters are divinylchlorophyll a and b. It also appears that the di/monocarboxylic monovinyl and divinyl biosynthetic routes lead to the formation of different pigment proteins in different greening groups of plants, and that the more highly evolved monovinylchlorophyll a biosynthetic route is associated with higher field productivity in wheat.
Chlorella↗
Chloroplast biogenesis. Detection of monovinyl protochlorophyll(ide) b in plants.
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.
Chlorophyll↗