Cellular compartmentalization

Kiipper H, Zhao F J, McGrath SP. Cellular compartmentation of zinc in leaves of the hyperaccumulator Thlaspi caerulescens. Plant Physiol 1999 119 305-311. 

Figure 2.2 The spontaneous self-aggregation of membranogenic surfactants into a vesicle, with an interior water pool that can host water-soluble molecules. If this self-aggregation takes place also in the presence of hydrophobic molecules, and/or ionic molecules, these can organize themselves into the bilayer or on the surface of the vesicle. A realistic scenario of the emergence of life can be based on a gradual transition from random mixtures of simple organic molecules to spatially ordered assemblies, displaying primitive forms of cellular compartmentation, selfreproduction, and catalysis.

In spite of these limitations to our complete knowledge of starch biosynthesis, information about the pathway of starch biosynthesis gained from studies of maize endosperm mutants can probably be generalized to other plant species because related mutants have occurred in peas, sorghum, barley, rice and Chlamydomonas, and because the same enzymes are found in starch-synthesizing tissues in other plant species. Variation in the number of isozymes and their developmental expression, and variations in cellular compartmentation, however, could result in a range of pathways with significant differences. 

Biosynthesis of IAA from tryptophan uses the L-form of the amino acid.75 Some of the enzymes that catalyze the conversion of specific intermediates have been identified, and some of the genes coding for the enzymes have been cloned. Such findings establish that plants are competent to carry out such metabolic conversions however, the specific involvement of these genes and intermediates requires confirmation, because biochemical studies carried out with applications to tissue segments or with extracts could disrupt tissue and cellular compartmentalization and because enzymes that catalyze the conversion of tryptophan to IAA in vitro may never come into contact with the intermediates in vivo. Thus, the physiological relevance of some of these pathways remains an open question.69 An additional concern is that many of the enzymes have wide substrate specificities, so it has been difficult to implicate them solely in IAA biosynthesis. Some of the intermediates and enzymes that have been described to have the competence to carry out these reactions are discussed below. 

Leegood, R. C. 1985. The inter-cellular compartmentation of metabolites in leaves of Zea mays. Planta. 164,163-171. 

Regulation by relocation. Mechanisms to overcome cellular compartmentalization are pivotal points of regulatory control. Relocation may involve targeting proteins. Targeting subunits guide both protein kinases and phosphatases to their substrates, located in different subcellular compartments. 

During the light period, when COi is being fixed in the chloroplasts by the RPP pathway, it is likely that the mechanisms discussed above for C3 photosynthesis are also functional in CAM plants [19]. Additional control mechanisms are expected to provide for the efficient functioning of the diurnal cycle of CO2 fixation. The functioning of CAM cannot, however, be interpreted solely in terms of enzymolo-gy, but rather will involve cellular compartmentation of enzymes and metabolites together with intracellular transport processes [17]. 

Cellular compartmentalization has inspired a range of new, and potentially useful, in vitro systems that treat droplets of water as microreactors. These have been recently reviewed by Griffiths and coworkers.298 The first DNA-display experiments, using this idea, were reported by Tawfik and Griffiths, who developed an in vitro compartmentalization (IVC) method using water-in-oil emulsions, which can be cheaply manufactured from oil, emulsifier, and detergent. By carefully selecting the conditions, a DNA library can be spatially arrayed by... 

Some areas of research of special interest on this molecule are glutathionylation of proteins, the cellular compartmentation and the role of this interesting molecule in disease. 

Studies aiming to solve the importance of the cellular compartmentation of glutathione are a very interesting field of research, as pointed out by Sies [6]. 

Sine, P. (1980). General principles of cellular compartmentation. In Cell Compartmentation and Metabolic Channelling (Nover, L., Lynen, F., Mothes, K eds.), pp. 17-32, Elsevier/North-Holland, New York. 

Discoloration of lightly processed fruits and vegetables is often the factor that determines their shelf-life. Enzyme catalyzed reactions which convert phenolic compounds to brown melanins are the main causes of discoloration of lightly processed fruits and vegetables. When products are peeled, cut, or otherwise injured, cellular compartmentation is lost, enzymes and substrates come in contact with each other, and discoloration occurs (10). The products of these reactions may also produce off-flavors, but the appearance is usually unacceptable at... 

Our defenses against oxygen toxicity fall into the categories of antioxidant defense enzymes, dietary and endogenous antioxidants (free radical scavengers), cellular compartmentation, metal sequestration, and repair of damaged cellular components. The antioxidant defense enzymes react with ROS and cellular products of free radical chain reactions to convert them to nontoxic products. Dietary antioxidants, such as vitamin E and flavonoids, and endogenous antioxidants, such as urate, can... 

Electron microscope studies of paraquat-treated leaves showed that after a few hours, membranes had been disrupted and cellular compartmentalization was destroyed. Experiments demonstrating the release of potassium from treated tissue as an indication of plasmalemma and tonoplast disruption (25)... 

Cellular Compartmentation of Herbicides. For detailed mechanism of action research, the Jja situ tissue distribution of DPE s should be known. One method to determine location is to treat with radiolabeled herbicide and, at some later time, fractionate the tissue into its various subcellular components... 

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