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The metabolism of plants grown in the cultivation medium is influenced by its composition and availability of CO2. In this project the effect of cultivation medium on the activity phosphoenolpyruvate carboxylase (PEPC, EC 4.1.1.31), NADP-malic enzyme (NADP-ME, EC 1.1.1.40), pyruvate, phosphate dikinase (PPDK, EC 2.7.9.1) and enzymes of nitrogen metabolism: nitrate reductase (NR, EC 1.7.1.1), glutamine synthetase (GS, EC 6.3.1.2), glutamate synthase (GOGAT, EC 1.4.1.13) and glutamate dehydrogenase (GDH, EC 1.4.1.2) was studied. The tobacco plant Nicotiana tabacum L., cv. Petit Havana SR1 were grown in vitro in containers fitted with a filter, which caused limited access of CO2. The cultivation medium was modified Murashige-Skoog agar with decreased amounts of phosphate, nitrate, ammonium, or with casein as source of nitrogen and with or without of 1.5% sucrose as additional carbon source Activity of PEPC was higher in plants grown in medium in the presence of sucrose. Reduced concentrations of phosphates, nitrates or NH4 + ions or when casein was the only source of N in medium caused decreased activity of PEPC. Under these conditions, also activity of NADP-ME and of enzymes of nitrogen metabolism: NR, GS decreased. Activity of all enzymes was also negatively affected by limited CO2. On the other...

Phosphoenolpyruvate carboxylase (EC 4.1.1.31; PEPC) plays many roles in plants; it connects the metabolism of saccharides and amino acids. PEPC is regulated at many levels including phosphorylation of serine residue near N-terminus. The aim was to found out, if the composition of cultivation medium affects the activity of PEPC and metabolically related enzymes such as NADP-malic enzyme (EC 1.1.1.40), pyruvate, phosphate dikinase (EC 2.7.9.1; PPDK) and enzymes participating in nitrogen assimilation, thus nitrate reductase (EC 1.7.1.1; NR), glutamine synthetase (EC 6.3.1.2; GS), glutamate synthase (EC 1.4.1.14; GOGAT), NAD-glutamate dehydrogenase (1.4.1.2; NAD-GDH) and NADP-glutamate dehydrogenase (1.4.1.4; NADP-GDH). Tobacco plants (Nicotiana tabacum L., cv. Petit Havana SR1) were grown in vitro in Murashige-Skoog agar. The effect of the presence of 2% succrose, reduced content of nitrogen compounds or phosphate and limited supply of CO2 was followed. Sucrose added to Murashige-Skoog medium caused the increase of enzyme activity of PEPC, NADP-ME and most of enzymes related to nitrogen uptake and metabolism - NR, GS, GOGAT, NAD-GDH a NADP-GDH. Reduced content of nitrogen compounds and phosphate in cultivation medium decreased activity of all monitored enzymes. Enzyme activities were also affected by the...

EEffffeecctt ooff ddrroouugghhtt oonn tthhee mmeettaabboolliissmm ooff ttaabbaaccccoo ppllaannttss (Nicotiana tabacum L.) Diploma thesis - abstract Lucia Miedzińska, Bc. Work Supervisor: Doc. RNDr. Helena Ryšlavá, CSc. Consultant: RNDr. Veronika Doubnerová, PhD. Drought stress is one of the most frequent form of plant stress, which occurs not only under condition of limited water availability, but also under reduced ability to accept water by roots, for example in salted or cold soils. In this thesis the changes in enzyme activities of: NADP-malic enzyme (EC 1.1.1.40; NADP-ME), phosphoenolpyruvate carboxylase (EC 4.1.1.31; PEPC) and pyruvate, phosphate dikinase (EC 2.7.9.1; PPDK) in tobacco plants (Nicotiana tabacum L., cv. W38) after drought were investigated. Enzyme activities in tobacco leaves were significantly increased during 11 days of stress, PEPC 2-fold, PPDK 3,3- fold and NADP-ME 4-fold compared to control plants. The regulation of NADP-ME and PEPC activities were studied on transcriptional level - by the real-time PCR method and on translational level - immunochemically. The expression of NADP-ME protein and transcription of mRNA for chloroplast NADP-ME isoform were increased, but mRNA for cytosolic isoform was not affected. The protein expression of PEPC was slightly increased, transcription of...