Chlorophyll synthesis

Research output: Chapter in Book/Report/Conference proceedingChapter

Abstract

Chlorophyll is the dominant pigment in a mature plant cell, whether in the leaf of a plant or in the abundant algal species. Chlorophyll is synthesized within the chloroplast from a plentiful precursor, the amino acid glutamate. From glutamate to the tetrapyrrole protoporphyrin IX, at which the pathway branches between chlorophyll and heme, the reactions occur in the plastid stroma and are catalyzed by soluble enzymes. The latter steps to chlorophyll, the first being the insertion of the central magnesium atom, occur with enzyme complexes that are at least partially if not entirely localized on membranes. Magnesium chelatase, the key enzyme in this pathway, is a complex of proteins that includes soluble and membrane-bound subunits. Subsequent reactions occur primarily on membranes and involve modification of structural groups on the periphery of the molecule. The pentultimate precursor of chlorophyll, protochlorophyllide, is reduced by NADPH to chlorophyllide in the only reaction in the pathway that requires light. This reaction, which in angiosperms is catalyzed by light-dependent NADPH:protochlorophyllide oxidoreductase, dramatically changes the property of the molecule and allows the product chlorophyllide, and its esterified product, chlorophyll, to interact with proteins. These chlorophyll-protein complexes become the building blocks of the photosynthetic apparatus. The biosynthetic pathway is tightly regulated, particularly at the key reactions that generate 5-aminolevulinic acid, magnesium-protoporphyrin IX and chlorophyllide. Expression of genes encoding critical enzymes is usually regulated markedly by light, and the activities of the enzymes are also regulated by end-products in typical feedback inhibition.
Original languageEnglish
Title of host publicationThe Structure and function of plastids
EditorsRobert R. Wise, J. Kenneth Hoober
Place of PublicationDordrecht, The Netherlands
PublisherSpringer, Springer Nature
Pages295-313
Number of pages19
ISBN (Print)9781402040610
DOIs
Publication statusPublished - 2006

Publication series

NameAdvances in photosynthesis and respiration
PublisherSpringer
Volume23
ISSN (Print)1572-0233

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