Magnesium protoporphyrin, formation

The biochemical conversion of magnesium protoporphyrin mono-methylester to protochlorophyll probably also involves the primary formation of a jr-cation radical [Cox (41)]. Whether the hydrogenation of protochlorophyll to chlorophyll involves phlorin intermediates [Woodward (214)] is still not known. 

Biosynthesis.—Further evidence has been adduced for the formation of 5-ALA and magnesium protoporphyrin-IX from glutamate in greening plants,and the enzymic preparation of the monomethyl ester of magnesium protoporphyrin has been described." Intermediates in the last stages of chlorophyll biosynthesis in which the geranylgeranyl side-chain is converted into phytyl have been studied l- C-labelled acetate is incorporated into the expected alternate positions in the phytyl ester side-chain (as shown by C n.m.r. spectral studies), but only low incorporations of mevalonate were obtained, presumably because of poor transport into the cell. The biosynthesis of chlorophyll-f has also been studied." ... 

Protoporphyrin IX is the starting material for the synthesis of the iron- and magnesium-containing porphyrins of the heme and chlorophyll types. In the formation of chlorophyll a the propionyl side chain of ring C is methylated and a new five-membered ring is formed (protochlorophyllide a). Reduction of ring D and ester formation with phytol (D 6.3) yields chlorophyll a. 

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