Chlorophyllase activity in developing leaves of Phaseolus vulgaris L.

In crude extracts of primary leaves from dark grown seedlings of Phaseolus vulgaris L., relatively high hydrolytic activity of chlorophyllase (chlorophyll-chlorophyllido-hydrolase, EC 3.1.1.14) was observed. When plants were exposed to continuous illumination, the enzyme activity in the extracts was doubled within 3 days and both chlorophyll a and b were synthesized. However, when exposed to periodic illumination (1 min light-59 min dark) the enzyme activity was doubled within 1 to 2 days and chlorophyll a was synthesized but the formation of chlorophyll b was suppressed. When plants were transferred from periodic illumination to continuous illumination chlorophyll b was synthesized but the activity of chlorophyllase declined. Chloramphenicol blocked the increase in enzyme activity independent of the light regimes, but cycloheximide inhibited the activity more effectively during growth in the light. The presence of chlorophyllase activity in the leaves is discussed in relation to the chlorophyll-proteins and the membranes known to be present in chloroplasts. It is suggested that the enzyme is synthesized on plastid ribosomes.