Capacity of Enzymes of the Euphorbiacea Aleurites montana Involved in C 0 2- Fixation, Compared to Plants Having C3-, C4- and Crassulacean Acid Metabolism

Norbert Grotjohann3, Ping H eb and Georg H. Schmid3-* a Lehrstuhl für Zellphysiologie, Fakultät für Biologie, Universität Bielefeld, Postfach 10 01 31, 33501 Bielefeld, Bundesrepublik Deutschland. Fax: +49 (521) 1066410. E-mail: [email protected] b Central South Forestry University, Zhuzhou/Hunan 41206, People’s Republic of China * Author for correspondence and reprint requests Z. Naturforrsch. 55c, 383-391 (2000); received March 2/April 7, 2000 Dedicated to Professor Wilhelm Menke on the occasion o f his 90th birthday Aleurites montana, Phosphoenolpyruvate Carboxylase, Malic Enzyme, Malate Dehydrogenase, Ribulose Bisphosphate Carboxylase Capacities of phosphoenolpyruvate carboxylase (PEP-Co), ribulose bisphosphate carbox­ ylase (Rubisco), NADP+ malic enzyme (ME) and of malate dehydrogenase (MDH) were measured in the Euphorbiacea Aleurites montana, grown under 700 ppm C 0 2 for four weeks prior to enzyme extraction. For comparison Bryophyllum daigremontiana (CAM), Saccharum officinarum (C4) and Capsicum frutescens (C3) were treated in the same way. PEP-Co capac­ ity of Aleurites was in the range of 12-, that of Capsicum approx. 26 nmol x min-1 x mg protein-1, without significant influence of the light period or C 0 2-treatment. In contrast, the activity of the enzyme from Saccharum was. depending on the duration of light, 160respec­ tively 96 times higher than that of the tung-oil tree. In Bryophyllum a rather low activity in the morning was increased during the day to approx. 230 nmol x min-1 x mg protein-1 in plants grown in the greenhouse and to approx. 115 nmol x min-1 x mg protein-1 in those from the growth chamber. Malate was hardly detectable in extracts of Aleurites, whereas it was high in Bryophyllum , depending on the light period. The ratio of average PEP-Co to Rub-Co capacity was high for the CAM-plant (20:1), somewhat lower for sugar cane (10:1), but almost at equality for Aleurites (0.9:1) and chilli (0.8:1). For the NADP+ malic enzyme, low capacity (20 to 28 nmol x min-1 x mg protein-1) was found for Aleurites and for Capsi­ cum!, whereas it was 10 to 17 times higher in Saccharum. In Bryophyllum , the activity was up to 80 nmol x min-1 x mg p r o te in , dependent on light period. MDH capacity was ex­ tremely high in all plants investigated. Highest rates (10-20 |j,mol x min-1 x mg protein-1), were obtained for Bryophyllum , followed by sugar cane and Capsicum with 5 -8 [.imol x min-1 x mg protein-1. Again, the lowest capacity was found in extracts of Aleurites with approx. 1.3 to 1.6 ^unol x min-1 x m protein-1. Thus, in Aleurites montana no indication for C4or Crassulacean acid metabolism was obtained. Therefore, the earlier observed very efficient uptake of C 0 2 cannot be explained by a high expression of the PEP-Co protein, known to occur in CAMand C4-plants.