[Investigation on the regulation of the glycolate-2,6-dichlorophenolindophenol oxidoreductase activity during greening of a Chlorella mutant].

We have examined the activity and regulation of the glycolate oxidizing enzyme in ten different greening stages of the Chlorella mutant Chlorella fusca C-1.1.10.10 The mutant has lost the ability to form chlorophyll in the dark. The dark grown cells exposed to light need after a short lag phase about 12 hs for normal greening. CO2-fixation starts after 2 h of illumination.In the first 2 h of illumination we find a phenomenon in the induction of the enzyme activity. In the first hour the activity increases to a maximum and then decreases in the second hour to a minimum. After a recovery time the activity increases proportionally to the time of illumination and finally reaches a value about 8 times higher than that found in the normal Chlorella strain.These results are discussed with respect to a dual mechanism in the regulation of the enzyme activity. At the beginning the glycolate oxidation may be regulated by phytochrome and then by a substrate induction.