Biosynthesis of chlorophyll b and the chlorophyll cycle.

Recent progress in the knowledge of chlorophyll b biosynthesis from chlorophyllide a and reduction of chlorophyll b to chlorophyll a is described. The minireview includes a description of the enzymes involved in these reactions and, where appropriate, of the genes encoding these enzymes. The possible physiological role of the mutual transformation of chlorophylls a and b (chlorophyll cycle) and the evolution of chlorophyll b formation are discussed.