Studies on 4-vinyl protochlorophyllide reductase and the biological significance of the divinyl and monovinyl monocarboxylic chlorophyll a biosynthetic routes
Fasoula, Dionysia Apostolos
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https://hdl.handle.net/2142/22004
Description
Title
Studies on 4-vinyl protochlorophyllide reductase and the biological significance of the divinyl and monovinyl monocarboxylic chlorophyll a biosynthetic routes
Author(s)
Fasoula, Dionysia Apostolos
Issue Date
1994
Doctoral Committee Chair(s)
Rebeiz, Constantin A.
Department of Study
Crop Sciences
Discipline
Crop Sciences
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Molecular
Biology, Plant Physiology
Language
eng
Abstract
Monovinyl chlorophyll a is the end product of chlorophyll a biosynthesis in higher plants. Most of the monovinyl chlorophyll a is formed via two major biosynthetic routes, the divinyl and monovinyl monocarboxylic routes which appear to be linked at various levels of chlorophyll precursors. The enzymes responsible for the conversion of the divinyl to monovinyl route are 4-vinyl reductases. The 4-vinyl protochlorophyllide a reductase converts divinyl protochlorophyllide to monovinyl protochlorophyllide.
In this thesis, the biological significance of the two monovinyl chlorophyll a biosynthetic routes is investigated. Studies involve a comparison of various physical-electronic properties of the divinyl and monovinyl protochlorophyllide a via three-dimensional molecular modelling and in vitro work with the enzyme 4-vinyl protochlorophyllide reductase. It appears that the reduction occurring at the level of protochlorophyllide is not the prominent point linking the two routes. Studies are extended to investigation of the differential incorporation of the monovinyl chlorophyll a that forms via either of the two routes into pigment-protein complexes in the thylakoid membranes. The relationship of the two routes with increased field yield of various species is also investigated and is shown that selection for yield in wheat and corn favors the monovinyl monocarboxylic chlorophyll a biosynthetic route at the end of the dark phase of the photoperiod. It is proposed that the monovinyl route represents a biosynthetic shortcut favorable to plants.
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