Stress enzyme

Diarrhea is defined as frequent liquid stools that can be caused by foods, fecal impaction, bacteria Escherichia coli, Salmonella), virus parvovirus, rotavirus), toxins, drug reaction, laxative abuse, malabsorption syndrome caused by lack of digestive enzymes, stress and anxiety, bowel tumor, and inflammatory bowel disease such as ulcerative colitis or Crohn s disease. 

The anthrax toxin is a tripartite toxin and consists ofthe binding component protective antigen (PA), the lethal factor (LF), which is a metalloprotease, and the edema factor (EF), which is a calmodulin-dependent adenylyl-cyclase. Both enzyme components are translocated via PA into target cells. PA is activated by furin-induced cleavage and forms heptamers, which are similar to the binding components of C2 toxin and iota toxin. In the low pH compartment of endosomes, the heptamers form pores to allow translocation of LF and EF. LF cleaves six of the seven MEKs (MAPK-kinases) thereby inhibiting these enzymes. The functional consequence is the blockade of the MAPK pathways that control cell proliferation, differentiation, inflammation, stress response, and survival. Whether this is the reason for the LT-induced cell death of macrophages is not clear [1]. 

Plants are constantly subject to adverse environmental conditions such as drought, flooding, extreme temperatures, excessive salts, heavy metals, high-intensity irradiation and infection by pathogenic agents. Because of their immobility, plants have to make necessary metabolic and structural adjustments to cope with the stress conditions. To this end, the expression of the genetic programme in plants is altered by the stress stimuli to induce and/or suppress the production of specific proteins which are either structural proteins or enzymes for specific metabolic pathways. 

An intriguing stress-induced alteration in gene expression occurs in a succulent plant, Mesembryanthemum crystallinum, which switches its primary photosynthetic CO2 fixation pathway from C3 type to CAM (Crassulacean acid metabolism) type upon salt or drought stress (Winter, 1974 Chapter 8). Ostrem et al. (1987) have shown that the pathway switching involves an increase in the level of mRNA encoding phosphoenol-pyruvate carboxylase, a key enzyme in CAM photosynthesis. 

Mayoral, M.L., Atsmon, D., Gromet-Elhanan, Z. Shimshi, D. (1981). Effect of water stress on enzyme activities in wheat and related wild species Carboxylase activity, electron transport and photophosphorylation in isolated chloroplasts. Australian Jourrml of Plant Physiology, 8, 385-94. 

Koch, G., Wells, R. Grisebach, H. (1987). Differential induction of enzyme in soybean cell cultures by elictor or osmotic stress. Planta, 171, 519-24. 

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