[Photosynthetic carboxylation pathways of differently pigmented Anacystis cells].

CO2 exchange, (14)CO2 fixation and (14)C-labelled photosynthetic products of differently pigmented Anacystis nidulans (strain L 1402-1) were studied during the induction period at +30°C. The algae were grown at +35° C in an atmosphere of 0.04 vol.-% CO2 and measured under the same low CO2 concentrations. Changing the culture conditions caused alterations in the pigment composition. Under "normal" illumination (white light; 0.6×10(3) erg/ cm(2) s) the relation between amounts of chlorophyll a and phycocyanin was 1:7 to 1:10. In a high light intensity (30.8×10(3) erg/cm(2) s) the phycocyanin content was reduced (1:5 to 1:2). When the cells were grown in red light of high intensity (20×10(3) erg/ cm(2) s) phycocyanin synthesis increased; the pigment ratio varied between 1:20 and 1:33. Anacystis cells grown under strong white light were filamentous.Photosynthetic CO2 uptake, measured with an infrared gas analyzer, was very low in algae grown in high light intensity. The pattern of (14)C-labelled photosynthetic products of these algae was very similar to those of the Calvin cycle. In Anacystis cells grown under low intensities of white light or in red light (14)CO2 was, at the beginning of the light period, incorporated mainly into aspatate and glycerine/serine. The enzyme activities of NAD(+)-specific malate dehydrogenase, ribulose-1,5-diphosphate carboxylase, aspartate and alanine aminotransferase decreased with increasing phycocyanin content. NADP(+)-specific malic enzyme activities showed practically no change. In contrast, phosphoenolpyruvate carboxylase activity increased with a higher rate of phycocyanin synthesis. In another series of experiments the behaviour of the PEP carboxylase activity after breakdown of the Anacystis cells was tested in differently pigmented cultures. In all cases the enzyme activities very rapidly decreased within two hours. The results obtained are discussed with reference to the correlation of pigment composition and CO2 fixation of the phosphoenolpyruvate system.