Regulation of Tetrapyrrole Synthesis in Developing Chloroplasts

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This research will examine chloroplastic ALA synthesis as a heterogenous phenomenon, whereby, two ALA-forming systems must be present, one of which makes ALA that is destined to protochlorophyllide (Pchlide), while the other fills up a pool that does not contribute to the Pchlide pathway and that could possibly be involved in heme synthesis. This study will identify one ALA pool as the precursor of Pchlide and the other ALA pool as the precursor of protoheme. Therefore, it will be proven that the branching point between the Mg and the Fe tetrapyrroles is not located at protoporphyrin, as generally thought, but at the synthesis of ALA itself.%%% For a number of years it has been axiomatic that the coarse control of chlorophyll synthesis lies at the level of 5- aminolevulinic acid (ALA). ALA synthesis is the crucial point in the regulation of chlorophyll as well as the pyrrole compounds. This study approaches the regulation of ALA from a physiological perspective but using biochemical tools. The relationship between the various metabolites that are formed from ALA in developing photosynthetic tissue will be determined.***//