Ornithine and arginine decarboxylase activities and effect of some polyamine biosynthesis inhibitors on Gigaspora rosea germinating spores

The pathways for putrescine biosynthesis and the effects of polyamine biosynthesis inhibitors on the germination and hyphal development of Gigaspora rosea spores were investigated. Incubation of spores with different radioactive substrates demonstrated that both arginine and ornithine decarboxylase pathways participate in putrescine biosynthesis in G. rosea. Spermidine and spermine were the most abundant polyamines in this fungus. The putrescine biosynthesis inhibitors alpha-difluoromethylarginine and alpha-difluoromethylornithine, as well as the spermidine synthase inhibitor cyclohexylamine, slightly decreased polyamine levels. However, only the latter interfered with spore germination. The consequences of the use of putrescine biosynthesis inhibitors for the control of plant pathogenic fungi on the viability of G. rosea spores in soil are discussed.     

Localization of arginine decarboxylase in tobacco plants

The lack of knowledge about the tissue and subcellular distribution of polyamines (PAs) and the enzymes involved in their metabolism remains one of the main obstacles in our understanding of the biological role of PAs in plants. Arginine decarboxylase (ADC; EC 4.1.1.9) is a key enzyme in polyamine biosynthesis in plants. We have characterized a cDNA coding for ADC from Nicotiana tabacum L. cv. Petit Havana SR1. The deduced ADC polypeptide had 721 amino acids and a molecular mass of 77 kDa. The ADC cDNA was overexpressed in Escherichia coli , and the ADC fusion protein obtained was used to produce polyclonal antibodies. Using immunological methods, we demonstrate the presence of the ADC protein in all plant organs analysed: flowers, seeds, stems, leaves and roots. Moreover, depending on the tissue, the protein is localized in two different subcellular compartments, the nucleus and the chloroplast. In photosynthetic tissues, ADC is located mainly in chloroplasts, whereas in non-photosynthetic tissues the protein appears to be located in nuclei. The different compartmentation of ADC may be related to distinct functions of the protein in different cell types.     

Ornithine decarboxylase activity in rat organs and tissues under artificial hypobiosis

The influence of hypothermia-hypoxia-hypercapnia on ornithine decarboxylase (ODC, EC 4.1.1.17) activities in rat organs and tissues and also on the thymocyte distribution throughout the cell cycle stages was studied. The state of artificial hypobiosis in rats on decrease in the body temperature to 14.4–18.0°C during 3.0–3.5 h was accompanied by drops in the ODC activities in the neocortex and liver by 50–60% and in rapidly proliferating tissues (thymus, spleen, and small intestine mucosa) by 80% of the control value. In kidneys the ODC activity raised to 200% of the control level. Twenty-four hours after termination of the cooling and replacing the rats under the standard conditions, the ODC activities in the neocortex, liver, kidneys, spleen, and intestinal mucosa returned to the control values, but remained decreased in the thymus. Forty-eight hours later the ODC activities in the thymus and spleen exceeded the normal level. The distribution of thymocytes throughout the cell cycle stages did not change in rats in the state of hypothermia (hypobiosis); 24 and 48 h after termination of the cooling the fraction of thymocytes in the S stage was decreased and the fraction of the cells in the G₀+G₁ stage was increased. The normal distribution of thymocytes throughout the cell cycle stages recovered in 72 h. Thus, in the thymus the diminution of the ODC activity preceded the suppression of the cell proliferation rate. The tissue-specific changes in the ODC activity are suggested to reflect adaptive changes in the functional and proliferative activities of organs and tissues during the development of hypobiosis under conditions of hypothermia-hypoxia-hypercapnia.     

Ornithine and S-adenosylmethionine decarboxylase activities and polyamine contents in developing muscle tissues and primary cultures of normal and polymyopathic hamsters

Polyamine (putrescine, spermidine, and spermine) contents and ornithine (ODC) and S-adenosylmethionine (SAMDC) decarboxylase activities have been assessed in an age-dependent manner, in normal and polymyopathic (dystrophic) hamster skeletal muscle, heart, and tongue extract and in primary tongue myoblast and skin fibroblast cultures. At 2 weeks of age, polyamine contents were significantly elevated in all of the dystrophic hamster tissues studied when compared with their age-matched controls. The degree of this elevation decreased with the age of the animals, generally, to a level where no significant difference in polyamine contents could be noted between normal and dystrophic hamster tissues. ODC and SAMDC activities in whole tissue extracts were consistently highest in 2-week-old muscle extracts and also declined with age. However, no significant changes in ODC or SAMDC activities were evident in any of the dystrophic muscle tissues studied when compared with their age-matched controls. Polyamine contents in dystrophic hamster myoblast and fibroblast primary cultures were also during proliferation (1 and 2 days after the initial seeding) compared with cultures prepared from normal hamsters. ODC and SAMDC activities in primary myoblast and fibroblast cultures clearly reflected the rate of cell proliferation, with highest activities found in subconfluent cell cultures. However, in general, no significant dystrophic-related abnormality in ODC or SAMDC activity was evident in proliferating myoblast or fibroblast cultures. These results suggest that the elevated polyamine contents of dystrophic hamster tissues and primary cultures may be due to a deficiency in polyamine catabolism or transport.     

鸟氨酸脱羧酶与肿瘤

多胺是广泛存在于哺乳类组织细胞中的小分子有机化合物,参与细胞的生长和分化等重要的生理过程,也是肿瘤细胞的快速生长所必需。鸟氨酸脱羧酶（omithine decarboxylase,ODC）是多胺合成代谢途径中的第一个限速酶,ODC活性的异常会引起包括肿瘤在内的一系列疾病的发生,由此该酶成为近年来研究的热点。简要综述了ODC与肿瘤关系的研究进展。     

Ornithine decarboxylase activity in lymphoid tissues of rats: Effects of glucocorticoids

The activity of ornithine decarboxylase was measured in several tissues of young female rats after treatment with cortisone acetate or dexamethasone. The expected increase in activity observed in liver and kidney was in marked contrast to the profound decrease found in thymus and spleen. Initially high activity in thymus was decreased to very low levels, sometimes below the limit of the assay procedure, 5 hours after treatment with dexamethasone or cortisone. There was also a large decrease in activity of the enzyme in spleen of hormone-treated rats. In both tissues, the marked effect was still evident 12 hours after treatment.     

Ornithine decarboxylase activity in rat tissues in the late periods after irradiation

Ornithine decarboxylase activity in some rat tissues was shown to grow at remote times after gamma irradiation (60Co) with nonlethal doses. The authors suggest that ornithine decarboxylase activity should be used as a biochemical marker of remote effects of ionizing radiation.     

Inducible overexpression of oat arginine decarboxylase in transgenic tobacco plants

To test the possible interaction of polyamines in plant growth responses, transgenic tobacco plants containing the Avena sativa L. (oat) arginine decarboxylase (ADC) gene under the control of a tetracycline-inducible promoter were generated. Inducible overexpression of oat ADC in transgenic tobacco led to an accumulation of ADC mRNA, increased ADC activity and changes in polyamine levels. Transgenic lines, induced during vegetative stage, displayed different degrees of an altered phenotype, the severity of which was correlated with putrescine content. These phenotypic changes were characterized by short internodes, thin stems and leaves, leaf chlorosis and necrosis, as well as reduced root growth. This is the first report to show altered phenotypes as a consequence of polyamine changes under tetracycline-induction in in vivo conditions. Interestingly, overexpression of oat ADC in tobacco resulted in similar detrimental effects to those observed by ADC activation induced by osmotic stress in the homologous oat leaf system. In the context of the role of specific polyamines in plant growth and development, the present results indicate that activation of the ADC pathway leading to high levels of endogenous putrescine (or its catabolytes) is toxic for the vegetative growth of the plant. In contrast, no visible phenotypic effects were observed in flowering plants following tetracycline induction. Further characterization of the different transgenic lines may shed light on the action of specific polyamines in different plant developmental processes.     

Ornithine decarboxylase activities of a Shewanella putrefaciens which produces only diamines

Ornithine decarboxylase (ODC) activity in cell extracts of Shewanella putrefaciens was surveyed. The pH dependency of the ODC activity revealed that the bacterium has two different ODC having optimum pH at 8·25 and 6·50. They were considered to be biosynthetic and biodegradative enzymes, respectively. Their activity ratio varied when the bacterium was cultured at pH 7·0 and 6·0. Both ODC activities were inhibited by α-difluoromethylornithine but cell growth was not affected.     

Ornithine decarboxylase in Paracoccidioides brasiliensis

Ornithine decarboxylase in Paracoccidioides brasiliensis, a dimorphic human pathogenic fungus, was more active at 37° C in the yeast phase and at 30° C in the mycelial phase. In contrast to other fungal systems, yeast growth and mycelium-to-yeast transition in P. brasiliensis were accompanied by a high activity of ornithine decarboxylase at the onset of the budding process, the activity of which was inhibited by 1,4-diamino-2-butanone. The activity of ornithine decarboxylase remained at a basal level during vegetative growth of both the mycelial phase and the late stage of yeast phase, and also through the yeast-to-mycelium transition. Received: 18 December 1995 / Accepted: 8 March 1996     

Photosynthetic activities of cadmium-treated tomato plants

Tomato plants (Lycopersicum esculentum Mill. cv. Moneymaker) grown on nutrient medium containing cadmium exhibit reduced net photosynthesis and reduced contents of chlorophyll and accessory pigments. In chloroplasts isolated from cadmiumtreated plants photosystem II activity, as measured by 2,6-dichlorophenolindophenol photoreduction, and photosystem II + I activity (H₂O → methyl viologen) were both inhibited to about 60%. When 1,5-diphenylcarbazide was used as artificial electron donor, no significant cadmium effect was observed. Photosystem I activity was not affected by cadmium. The fine structure of chloroplasts in cadmium-treated plants was degenerated, similarly to senescence response. The principal symptom of cadmium action was the occurrence of large plastoglobules and a disorganization of the lamellar structure, mainly grana stacks. Transfer of cadmium-treated plants into a medium with increased manganese level caused grana stacking and restoration of photosystem II activity.     

Ornithine decarboxylase and thymidine kinase activity in tissues of prolactin-treated rats: effect of hypophysectomy

The activities of ornithine decarboxylase and thymidine kinase were determined in tissues of young intact and hypophysectomized rats at various times after treatment with prolactin. In both types of animals, ornithine decarboxylase activity increased in liver, kidney, spleen and adrenal of prolactin treated rats. Thymidine kinase activity increased only in liver and spleen of intact rats. Increase in the kinase activity was smaller, and occurred later than the change in ornithine decarboxylase. In hypophysectomized animals, thymidine kinase activity increased in spleen, but not in liver, following prolactin treatment.     

Ornithine decarboxylase activity in insulin-deficient states

The activity of ornithine decarboxylase, the rate-controlling enzyme in polyamine biosynthesis, was determined in tissues of normal control rats and rats made diabetic with streptozotocin. In untreated diabetic rats fed ad libitum, ornithine decarboxylase activity was markedly diminished in liver, skeletal muscle, heart and thymus. Ornithine decarboxylase was not diminished in a comparable group of diabetic rats maintained on insulin. Starvation for 48h decreased ornithine decarboxylase activity to very low values in tissues of both normal and diabetic rats. In the normal group, refeeding caused a biphasic increase in liver ornithine decarboxylase; there was a 20-fold increase in activity at 3h followed by a decrease in activity, and a second peak between 9 and 24h. Increases in ornithine decarboxylase in skeletal muscle, heart and thymus were not evident until after 24–48h of refeeding, and only a single increase occurred. The increase in liver ornithine decarboxylase in diabetic rats was greater than in normal rats after 3h of refeeding, but there was no second peak. In peripheral tissues, the increase in ornithine decarboxylase with refeeding was diminished. Skeletal-muscle ornithine decarboxylase is induced more rapidly when meal-fed rats are refed after a period without food. Refeeding these rats after a 48h period without food caused a 5-fold increase in ornithine decarboxylase in skeletal muscle at 3h in control rats but failed to increase activity in diabetic rats. When insulin was administered alone or together with food to the diabetic rats, muscle ornithine decarboxylase increased to activities even higher than in the refed controls. In conclusion, these findings indicate that the regulation of ornithine decarboxylase in many tissues is grossly impaired in diabetes and starvation. They also suggest that polyamine formation in vivo is an integral component of the growth-promoting effect of insulin or some factor dependent on insulin.     

Ornithine decarboxylase activity in Helianthus tuberosus

Ornithine decarboxylase (ODC, EC 4.1.1.17) was studied in crude extracts of parenchyma slices of dormant tubers activated for 12 h, tuber shoots and shoot apices. It was highest in shoot apices. The enzyme activity was measured by the production of ¹⁴CO₂ from labelled ornithine; V_max was 450 nmol (mg protein)^-1h^-1, K_m for ornithine and pyridoxal phosphate were, respectively, 30 m M and 5μ M . Only when partially purified, the ¹⁴CO₂ production was inhibited by α-difluoromethylornithine, while in crude extracts dithiothreitol was inhibitory. Ornithine and arginine decarboxylase (ADC, EC 4.1.1.19) activities from parenchyma tubers were not greatly altered by exogenously supplemented ornithine, even though its endogenous pool increased. Exogenously supplemented arginine enhanced ornithine decarboxylase activity, whereas putrescine decreased it slightly. The possibility of artifactual activities in the crude extract is also discussed.     

Photosynthetic activities of vegetative and fruiting tissues of tomato

Photosynthetic activities of different chlorophyll-containing parts of tomato plants (Lycopersicon esculentum Mill. cv. Saporo) were assessed using chlorophyll fluorescence techniques. Trusses selected for study contained near mature, green fruit and measurements were carried out on the truss peduncle, pedicels, calyces, and fruit. Activities of these tissues were compared with those of adjacent compound leaves considered to be the primary suppliers of photosynthetic assimilates to fruit. All tissues showed high intrinsic efficiencies of photosystem II, measured as FV/FM, in dark-adapted tissue (range 0.77-0.82). Maximal photosynthetic electron transfer activities varied from 110 to 330 mol m^-2 s^-1. With increasing photon flux density there was a gradation of tissue activity with actual photosynthetic yields, electron transport rates and photochemical quenching coefficients (qP) of tissues decreasing in the order: upper leaf lamina, lower leaf lamina, leaf petiole, truss peduncle, pedicel, calyx, and fruit. The reverse order was found for the rapidity at which absorbed photon energy was diverted to non-photochemical pathways as photon flux density was increased. The onset of FO quenching at high photon flux densities suggested that all tissues contained a regulated mechanism for dissipating excess energy as heat. It was concluded that the non-leaf green tissues of tomato are quite active photosynthetically and therefore potentially contribute significantly to plant growth. At a photon flux density of 185 mol m^-2 S^-1, 29% of photosynthetic electron transport activity on a surface area basis was located in tissues other than leaf laminae, with fruit accounting for 15%.