THE REGULATION OF ENZYMES INVOLVED IN CHLOROPHYLL BIOSYNTHESIS

All living organisms contain tetrapyrroles. In plants, chlorophyll (ch lorophyll a plus chlorophyll b) is the most abundant and probably most important tetrapyrrole. It is involved in light absorption and energy transduction during photosynthesis, Chlorophyll is synthesized from t he intact carbon skeleton of glutamate via the C-5 pathway. This pathw ay takes place in the chloroplast. It is the aim of this review to sum marize the current knowledge on the biochemistry and molecular biology of the C-5-pathway enzymes, their regulated expression in response to light, and the impact of chlorophyll biosynthesis on chloroplast deve lopment. Particular emphasis will be placed on the key regulatory step s of chlorophyll biosynthesis in higher plants, such as 5-aminolevulin ic acid formation, the production of Mg2+-protoporphyrin IX, and light -dependent protochlorophyllide reduction.