[Effect of red light on activity of cAMP phosphodiesterases in photoperiodically different cereals and vernalized winter wheat].

Red light illumination of seedlings of photoperiodically different cereals had a different effect on the activity of multiple cyclic adenosine monophosphate phosphodiesterases. The response of all phosphodiesterase forms was reversed in fully vernalized winter wheat Triticum aestivum L.

[Effect of vernalization and red light illumination of seedlings of bread wheat (Triticum aestivum L.) on the temperature profile of the cAMP phosphodiesterase activity]. / Vliianie iarovizatsii i osveshcheniia prorostkov miagkoi pshenitsy Triticum aestivum L. krasnym svetom na khod temperaturnoi krivoi fosfodiésterazy tsAMF.

Phenotypic manifestations of Vrn (vernalization) and Ppd (photoperiodism) genes responsible for transition of bread wheat Triticum aestivum L. to generative growth (flowering) are mutually related. Since the mechanism of phytochrome-induced photoperiodism involves the enzymes of cyclic adenosine monophosphate metabolism and phosphodiesterase in particular, we tested involvement of phosphodiesterase in the process of winter wheat vernalization and formation of flowering competence in alternate wheat requiring a long day but no vernalization for the transition to flowering. We studied temperature dependence of phosphodiesterase activity in vernalized and unvernalized winter wheat on the one hand and in etiolated and red light illuminated seedlings of alternate wheat on the other hand. Short-term experiments demonstrated that vernalization and red light illumination are similar to long day by the effect on the long-day plants. Both influences induced a pronounced inversion of the temperature profile of phosphodiesterase activity in the 28-45 degrees C range. We propose that phosphodiesterase is involved in vernalization processes and can serve as a sensor of low temperature in winter wheat. Changed temperature profile is a radical control mechanism of phosphodiesterase activity in response to the influences (red light and vernalizing temperatures) responsible for competence of various bread wheat forms for generative growth.

[Adenosine-3':5'-monophosphate phosphodiesterase from Rhizobium]. / Fosfodiésteraza adenozin-3':5'-monofosfata u Rhizobium.

The phosphodiesterase (PDE) activity of adenosine-3':5'-monophosphate was detected in the cells of tubercular bacteria of Rhizobium lupini and Rhizobium japonicum. The specific activity of three Rhizobium forms, e.g. bacteroids from lupine root tubercles, free-nitrogen-fixing culture and vegetative cells grown on a mannitol--yeast agar, were compared. In the bacteroids PDE is represented both by soluble and membrane-bound forms. The optimal enzyme activity is revealed in an alkaline medium, whereas the curve of PDE activity dependence on pH has a broad maximum. PDE is inhibited by methylxanthines, the inhibiting effect being stronger than that of theophylline.

[Effect of growth conditions on the activity of the enzymes of cyclic 3':5'-AMP synthesis and decay in phototrophic bacteria]. / Bliianie uslovii byrashchivaniia fototrofnykh bakterii na aktivnost' Fermentov sinteza i raspada tsiklicheskogo 3':5'-AMP.

Activity, ratio and summary content of cyclic AMP enzymes, adenylate cyclase and phosphodiesterase varied depending on growth conditions of phototrophic bacteria (Rhodospirillum rubrum and Rhodopseudomonas palustris). It suggests, that membrane-bound and soluble enzymes carry different functions. The increase of adenylate cyclase under chaning growth conditions was usually accompanied by the increase of phosphodiesterase. Sharp increase of both enzymes activity was observed when bacteria were growth in aerobic conditions. The activity of both enzymes in chromatophores was 2.8-fold higher when bacteria were grown in the light in anaerobic conditions, than in chromatophores of bacteria grown under stationary aerobic conditions in the light. It is suggested that 3':5' AMP can participate in autotrophic carbon assimilation or in the synthesis of pigments and other components of bacterial photosynthetizing apparatus. Substitution of NH4+ into NO3- and glutamate under the growing of R. rubrum in anaerobic conditions in the light resulted in the increase of the enzymes activities, which is the evidence of possible role of 3':5' AMP in mineral nitrogen uptake and nitrogen fixation. Glutamate concentration of 4 g/l stimulated the enzymes both in vivo and in vitro. The data obtained suggest that 3':5' AMP can carry multiple functions, participating in regulation of a number of metabolic processes in photorophic bacteria.

[Subcellular distribution and several properties of the cAMP enzyme system of phototrophic bacteria]. / Subkletochnoe raspredelenie i nekotorye svoistva fermentov sistemy cAMP u fototrofnykh bakterii.

In the cells of the phototrophic bacteria Rhodospirillum rubrum and Rhodopseudomonas palustris the two enzymes of the cAMP system enzymes - adenylate cyclase and cAMP phosphodiesterase (PDE) exist in a soluble and membrane-bound forms. After mild disruption of the cells (sonication up to 3 min) the activity of both enzymes is found in the chromatophores. In the cells of the two types of bacteria grown under anaerobic conditions soluble adenylate cyclase is predominant. In the cells of R. rubrum the soluble form of PDE posesses higher activity, whereas in the cells of Rh. palustris a higher activity is observed in the membrane-bound form. In addition to their different localization in the cells, the PDE forms of Rh. rubrum differ in their ratios to the concentrations of hydrogen ions and bivalent metals; the latter difference, however, may be accounted for by the effect of a protein modulator of PDE. The pH optimum of membrane-bound PDE is 9.15. Soluble PDE has two activity maxima at pH 7.5 and 8.7. It is probable that similar to the animal tissue enzyme, PDE from Rh. rubrum exists in the soluble phase in at least tw forms. Close pH optima for soluble adenylate cyclase and for one of the soluble PDE forms (about 8.5) may indicate the unidirectional control of these enzymes by hydrogen ion concentration.

[cAMP phosphodiesterase from phototrophic bacteria Rhodospirillum rubrum]. / Fosfodiesteraza 3',5'-AMP Fototrofnoi bakterii Rhodospirillum rubrum

cAMP phosphodiesterase activity is discovered in supernatant of R. rubrum cell homogenate after centrifugation at 1000 g. The enzyme is highly active (5.62 nmoles/mg of protein per 1 min) at a broad pH range--from 7.0 to 9.0. The enzyme activity is strongly inhibited with caffeine and dithiotreitol and very significantly inhibited by ascorbic acid. The dependence of the enzyme activity on the incubation time and protein and substrate concentrations in the reaction mixture is estimated. cAMP phosphodiesterase is found in soluble fraction and in particule fractions sedimenting at 30 000 g. The enzyme activity is completely absent in washed chromatophores sedimenting at 160 000 g.