Chlorophyll a is the primary form of chlorophyll in plants. Chlorophylls are pigments that give plants their perceived green colour and are essential for photosynthesis, the process by which light energy is converted into chemical energy. Chlorophyll a, in particular, absorbs energy from wavelengths of violet-blue and orange-red light. Two pathways exist for chlorophyll a biosynthesis whereby geranylgeranyl diphosphate and 3,8-divinyl chlorophyllide a becomes chlorophyll a. Both of these pathways take place in the chloroplast. This is the first pathway of chlorophyll a biosynthesis. The three reactions of the subpathway to synthesize phytyl diphosphate from geranylgeranyl diphosphate are catalyzed by the same enzyme, geranylgeranyl dehydrogenase. This enzyme converts geranylgeranyl diphosphate into dihydrogeranylgeranyl diphosphate, dihydrogeranylgeranyl diphosphate into tetrahydrogeranylgeranyl diphosphate, and tetrahydrogeranylgeranyl diphosphate into phytyl diphosphate. The only reaction in the subpathway to synthesize chlorophyllide a from 3,8-divinyl chlorophyllide a is catalyzed by 3,8-divinyl protochlorophyllide a 8-vinyl-reductase. Lastly, chlorophyll synthetase converts chlorophyllide into chlorophyll a. It requires a magnesium ion as a cofactor.

Chlorophyll a Biosynthesis I References