Biosynthesis of chlorophyll b in pigment mutant C‐2A′ of Scenedesmus obliquus

It is demonstrated that chlorophyll b does not only derive from chlorophyll a, but is also formed separately from an in vivo‐occurring chlorophyllide b. The branching point for the latter synthesis is at the level of chlorophyllide, since no protochlorophyllide b was detectable. We have indications that the enzyme oxidizing chlorophyll a to chlorophyll b accepts also non‐phytylated 17,18 dihydroporphyrins and is not restricted to chlorophylls. Preparations of chlorophyllide a and chlorophyll a could both be transferred with the same enzyme fraction to chlorophyllide b and chlorophyll b, respectively. Preliminary experiments show this enzyme to be membrane bound and light independent. An updated scheme for chlorophyll b biosynthesis is presented.