Characterization of carbamoyl phosphate synthetase of Streptomyces spp.

Carbamoyl phosphate synthetase (CPS) activity in Streptomyces lividans was repressed (70%) by addition of arginine and uracil in the growth medium. Enzyme activity was also inhibited by UMP and activated by ornithine and IMP. Pattern of inhibition and activation was similar irrespective of whether the cells were grown in medium supplemented with arginine or with uracil. A mutant of S. coelicolor with dual auxotrophy for arginine and uracil possessed only about 20% of CPS activity compared to the wild-type strain. An activity staining protocol has been developed for CPS enzyme. Using this method a single CPS band has been observed in the crude extracts of Escherichia coli as well as in S. lividans. Taken together, our results supported the conclusion that Streptomyces species might possess a single CPS enzyme unlike other gram-positive bacteria, which show the presence of two pathway-specific isozymes (Bacillus) or none (Lactobacillus and Leuconostoc).

Development of photosynthetic electron transport reactions under the influence of phytohormones and nitrate nutrition in greening cucumber cotyledons.

Development of the photosynthetic electron transport system, under the influence of hormones and nitrate-nutrition, in greening cucumber cotyledon was investigated. Both photosystems, PS I measured as DCPIP → MV, and PS II as H2O → pBQ, were significantly promoted by GA and kinetin with kinetin being more effective. PS II/PS I ratio, though increased in control, did not change significantly with GA or kinetin treatment. Other partial reactions (H2O → MV/K3Fe(CN)6/NADP) were also promoted. Addition of KNO3 showed concentration-dependent effects on growth and photosynthetic electron transport reactions (H2O → MV/K3Fe(CN)6/NADP). It is concluded that both hormones and nutritional status influence development of the photosynthetic electron transport system in greening cucumber cotyledons.