Determination of the activity of chlorophyll b to chlorophyll a conversion during greening of etiolated cucumber cotyledons by using pyrochlorophyllide b

To investigate the changes in the activity of the conversion of chlorophyll b to chlorophyll a during greening, pyrochlorophyll b was used as a substrate instead of chlorophyll b. Pyrochlorophyll b and pyrochlorophyll a accumulated after incubation of pyrochlorophyllide b with cucumber (Cucumis sativus L. cv. Aonagajibai) etioplasts. These observations indicate that structural variation on the isocyclic ring is tolerated by the enzymes responsible for the conversion of chlorophyll b to chlorophyll a. A small amount of pyrochlorophyll a was separated from chlorophyll a by high performance liquid chromatography, which enables us to determine the activity of chlorophyllide b to chlorophyll a conversion with chloroplasts which have a large amount of endogenous chlorophylls. By using pyrochlorophyllide b as a substrate, we showed that etioplasts have high activity before exposure to light.