 In most plants, chlorophyll is derived from glutamate and is synthesised along a branched pathway that is shared with heme and siroheme.The initial steps incorporate glutamic acid into 5-aminolevulinic acid (ALA); two molecules of ALA are then reduced to porphobilinogen (PBG), and four molecules of PBG are coupled, forming protoporphyrin IX.Chlorophyll synthase is the enzyme that completes the biosynthesis of chlorophyll "b" by catalysing the reaction 
This forms an ester of the carboxylic acid group in chlorophyllide "b" with the 20-carbon diterpene alcohol phytol.