Newly Discovered Intermediates in the Chlorophyll a Biosynthetic Pathway
Belanger, Faith Christine
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https://hdl.handle.net/2142/77653
Description
Title
Newly Discovered Intermediates in the Chlorophyll a Biosynthetic Pathway
Author(s)
Belanger, Faith Christine
Issue Date
1982
Department of Study
Plant Biology
Discipline
Botany
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Plant Physiology
Language
eng
Abstract
Several new intermediates in chlorophyll a biosynthesis were detected in higher plants and chemically identified. The newly discovered pigments are divinyl protochlorophyllide, divinyl protochlorophyllide ester, divinyl chlorophyllide a, divinyl chlorophyll a and monovinyl Mg-protoporphyrin-6-ester. Well-established chemical derivatization techniques coupled to absorption and fluorescence spectroscopy were used to identify the pigments. The spectra of the derivatized compounds exhibited the expected spectral shifts and were virtually identical to those of the appropriate standards. It has been proposed that these new pigments are intermediates in a four-branched chlorophyll a biosynthetic pathway (Rebeiz et al., 1981, In: Photosynthesis Vol. 5, Edited by Akoyunoglou, G., Int. Sci. Services. Balaban, Israel, pp. 197-212).
Divinyl protochlorophyllide and divinyl protochlorophyllide ester were shown to be directly phototransformable yielding divinyl chlorophyllide a and divinyl chlorophyll a, respectively. The phototransformation clearly demonstrated that these four newly discovered pigments are indeed involved in chlorophyll a biosynthesis. Light appeared to regulate the proportions of the monovinyl and divinyl components, but the effect varied with the plant species.
Duggan and Rebeiz (Plant Sci. Lett. 1982, in press) have demonstrated that the major fate of the newly formed divinyl chlorophyllide a is rapid conversion to monovinyl chlorophyllide a. The fate of the divinyl chlorophyll a formed from photoreduction of divinyl protochlorophyllide ester is not yet known. The role of the newly described monovinyl Mg-protoporphyrin-6-ester in chlorophyll a biosynthesis remains to be demonstrated.
In addition to the chemical identification of new chlorophyll a precursors, an investigation into the effects of axial ligation and low temperature on the spectroscopic properties of tetrapyrroles was reported.
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