For the regulation of photosynthesis at gene level, the genes encoding fructose-1,6-bisphosphate aldolase (ALD) and triosephosphate isomerase (TPI) were transferred into filamentous, heterocystour cyanobacterium Anabaena sp. PCC7120, which were from spinach and rice, respectively. Cells were grown in the medium supplemented with CO2. The growth parameters, photosynthesis, enzyme activity of ALD and TPI and carbonic anhydrases activities were measured and compared between transgenic and wild type cells. Transgenic cells had higher ALD and TPI enzyme activities than the wild type cells at all experiment conditions. Both cell growth and photosynthesis activities were improved under elevated CO2, especially for transgenic cells. Total intracellular CA activities were decreased with the increasing of NaHCO3 concentrations, and increased with the increasing of CO2 concentrations. Transgenic cells showed comparative advantages over the wild type cells in all experiments. These data indicated that the overexpress of foreign ALD and TPI affected the photosynthetic carbon fixation process through the accelerating of carbon flux. (C) 2004 Elsevier Inc. All rights reserved.