Roots surface enzymes

VAUGHAN D., ORD B.G. and MALCOLM R.E. 1978. Effect of soil organic matter on some root surface enzymes of and uptakes into winter wheat. Journal of Experimental Botany, 29, 1337-1344. 

This aspect has been investigated for invertase using intact wheat plants In this tissue, the sucrose substrate has access to only 50% of the total root invertase and this may in practice be regarded as a root surface enzyme. Nevertheless, HA inhibits this root surface enzyme in the intact plant to the same extent as it inhibits the total invertase in the tissue homogenate. Whether the tacit assumption can be made that HA influences enzymes generally in intact tissues awaits further clarification. 

APase in onion roots. Enzyme activity was mainly extracellular with the heaviest concentration in corner spaces between the epidermal and hypo-dermal layers. He suggested the possibility of a subcutaneous pore through which the enzyme could be released to the root surface. Bieleski and co-workers (Reid Bieleski, 1970 Bieleski Johnson, 1972) studied the psi induction and location of APase in duckweed (Spirodela oligorrhiza). APase in control plants was located primarily in and around the vascular strands. In P-deficient plants psi-APase activity was 10-20 times the control value. Enzyme activity was primarily located in the epidermis of the root and undersurface of the frond, the tissue locations most likely to provide access to phosphate esters in the medium. These workers further demonstrated that hydrolysis of organic phosphates occurred in the external medium and/or the apoplast followed by Pi uptake into the cell. 

Other plants such as potatoes, cauliflower, cherries, and soybeans and several fungi may also be used as sources of peroxidase enzymes. Soybeans, in particular, may represent a valuable source of peroxidase because the enzyme is found in the seed coat, which is a waste product from soybean-based industries [90]. In this case, it may be possible to use the solid waste from the soybean industry to treat the wastewaters of various chemical industries. In fact, the direct use of raw soybean hulls to accomplish the removal of phenol and 2-chlorophenol has been demonstrated [105]. However, it should be noted that this type of approach would result in an increase in the amount of solid residues that must be disposed following treatment. Peroxidases extracted from tomato and water hyacinth plants were also used to polymerize phenolic substrates [106], Actual plant roots were also used for in vivo experiments of pollutant removal. The peroxidases studied accomplished good removal of the test substrate guaiacol and the plant roots precipitated the phenolic pollutants at the roots surface. It was suggested that plant roots be used as natural immobilized enzyme systems to remove phenolic compounds from aquatic systems and soils. The direct use of plant material as an enzyme source represents a very interesting alternative to the use of purified enzymes due to its potentially lower cost. However, further studies are needed to confirm the feasibility of such a process. 

In some cases pectinolytic enzymes have been associated with virulence and it is generally accepted that pectinolysis by these bacteria facilitates their entry and spread in plant tissue. In Rhizohium, these enzymes may play a role in the root infection process that precedes nodule formation (Hubbell et al 1978). A. irakense has never been reported to be pathogenic on plants. It can therefore be speculated that moderate and strictly regulated pectinolysis of A. irakense facilitates entry in the outer cortex of plants roots, since A. irakense has been isolated from surface-sterilized roots. It is likely that breakdown of plant polysaccharides by root colonizing bacteria can provide them with extra carbon source. 

Phytostabilization on the root membranes. Proteins and enzymes directly associated with the root cell walls can bind and stabilize the contaminant on the exterior surfaces of the root membranes. This prevents the contaminant from entering the plant. 

Pfeifer, Wely, and Wippermann1671 examined surface portions of a lysozyme protein molecule. A fractal dimension of D = 2.17 was determined and related to the rate of substrate trapping at the enzyme active site. The root mean square substrate displacement via diffusion at the surface increases as time (t)1AD whereas surface capture of substrates is greater when compared with a smooth (D = 2) surface. From their results, the authors suggested that the observed value of D = 2.17 corresponds to an optimum overall capture rate. 

This scoring function showed a reliability of 1.5 kcal/mol when tested on eight protein-ligand complexes.200 The preference-based scoring scheme was used in docking experiments following a surface complementary screen. It was found that 20 rigid enzyme-inhibitor complexes could be reassembled with all-atom root-mean-square deviations of 1.0 A from the native complexes.129... 

Upon addition of an enzyme solution, a rapid decrease of resonator frequency is observed followed by a long period of the slower decrease (Fig. la). The adsorption of HRP on a PSS layer is essentially completed after 5-10 min. At the same time, the changes in series resonance resistance, which are proportional to the square root of density and viscosity of the media near the resonance surface [5], do not exceed 2 Ohm. It allows to consider the formed enzyme layers as a rigid and use the Sauerbrey equation to calculate the mass of the adsorbed HRP. 

In the complexes of RmL with inhibitors, the central, helical part of the lid (residues 85-92) is transported 8 A across the molecular surface (Fig. 9). During this change the helix actually rolls back from the active site, rotating by 167° about its own axis. This dramatic shift is a rigid body movement when the two helices, in the native and inhibited enzymes, are superimposed, the root-mean-square deviation for all main-chain atoms is 0.31 A, well within the accuracy limits imposed by the experimental methods used. 

Urea is not expected to adsorb to suspended solids and sediment. Volatilization from water surfaces is not expected. Urea is rapidly hydrolyzed to ammonia and carbon dioxide in environmental systems by the extracellular enzyme, urease, which originates from microorganisms and plant roots. 

For example, some plants can increase root volume and surface area to optimize uptake potential. Alternatively, plant roots and/or associated fungi can produce chelating compounds that solubilize ferric iron and calcium-bound phosphorus, enzymes and/or acids that solubilize phosphate in the root vicinity. Plants also minimize phosphorus loss by resorbing much of their phosphorus prior to litterfall, and by efficient recycling from fallen litter. In extremely unfertile soils (e.g., in tropical rain forests) phosphorus recycling is so efficient that topsoil contains virtually no phosphorus it is all tied up in biomass. 

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