Exoenzymes

Organisms that require compounds manufactured by other organisms are called hetei oti ophs (other-nourishing). Many heterotrophs secrete enzymes (exoenzymes) that hydrolyze large molecules such as starch and cellulose to smaller units that can readily enter the cell. 

The bacterial culture converts a portion of the supplied nutrient into vegetative cells, spores, crystalline protein toxin, soluble toxins, exoenzymes, and metabolic excretion products by the time of complete sporulation of the population. Although synchronous growth is not necessary, nearly simultaneous sporulation of the entire population is desired in order to obtain a uniform product. Depending on the manner of recovery of active material for the product, it will contain the insolubles including bacterial spores, crystals, cellular debris, and residual medium ingredients plus any soluble materials which may be carried with the fluid constituents. Diluents, vehicles, stickers, and chemical protectants, as the individual formulation procedure may dictate, are then added to the harvested fermentation products. The materials are used experimentally and commercially as dusts, wettable powders, and sprayable liquid formulations. Thus, a... 

The second type of material includes spores, which may or may not produce disease symptoms but which can germinate in the insect gut and give rise to vegetative bacterial cells which in turn may produce, and exoenzymes such as phospholipases (lecithinases) or hyaluronidase. The phospholipases may produce direct toxic symptoms owing to their action on nervous or other phospholipid-containing tissue. Hyaluronidase breaks down hyaluronic acid and produces effects on animal tissue which are morphologically similar to the breakdown of insect gut wall in the presence of microbial insecticide preparations. 

Heat-labile soluble toxin Exoenzymes (phospholipases, hyaluronidase) Vegetative bacterial cells... 

Palva TK, Holmstrom K-0, Heino P, PalvaET (1992) Induction of plant defence responses by exoenzymes of Erwinia carotvora subsp. carotovora. Mol Plant-Microbe Interact 6 190-196... 

Clearly, it is the exoenzymes that are of interest in textile processing, an area which has seen considerable development in recent years. Originally used only in the preparatory processes of scouring and desizing, they are now also used to modify textile surfaces in finishing as well as in effluent treatment. 

In this chapter we describe the use of pea seeds to express the bacterial enzyme a-amylase. Bacterial exoenzymes like the heat stable a-amylase from Bacillus licheni-formis are important for starch hydrolysis in the food industry. The enzymatic properties of a-amylase are well understood [13,14], it is one of the most thermostable enzymes in nature and it is the most commonly used enzyme in biotechnological processes. Although fermentation in bacteria allows highly efficient enzyme production, plant-based synthesis allows in situ enzymatic activity to degrade endogenous reserve starch, as shown in experiments with non-crop plants performed under greenhouse conditions [12,15]. Finally, the quantitative and sensitive detection of a-amylase activ-... 

However, in some situations, it can be assumed that the particulate substrate is completely covered with bacteria that excrete the exoenzymes. As it is assumed that enzymes are excessively present, the hydrolysis rate is constant per unit area available for hydrolysis, i.e., a surface-based kinetics model ... 

As indicated in Figure 3.4, the covalent bond, i.e., two common shared electrons, between two carbon atoms in the complex molecule is cleaved when initiated by the exoenzymes. The highly reactive intermediates that are formed react and produce new and stable bonds resulting in two new molecules that may undergo further hydrolysis. Hydrolysis is, thus, an important initial step in the transformation of complex organic matter present in a form that cannot directly be used at substrate. Hydrolysis is a process that—with different reaction rates — proceeds under aerobic, anoxic and anaerobic conditions. It is important to note that hydrolysis takes place without use of an electron acceptor. 

A r-(3-oxododccanoyl)-L-homoscrinc lactone, OdDHL or 30, C12-HSL Pseudomonas aeruginosa Virulence factors - alkaline protease, clatasc, exotoxin A, haemolysin, neuraminidase, exoenzyme S, Xcp secretion, RhlR, biofilm formation. 

For example, organic matter deeply embedded in the mineral matrix of biogenous hard parts would not be exposed to exoenzyme attack. This embedding could occur during deposition of the minerals or through adsorption of the organic matter from seawater. Most of the ballasting effect exerted on POM is conferred by calcareous and siliceous hard parts and by clay minerals. 

Any enzyme catalyzing a hydrolytic reaction that occurs within a polymeric substrate molecule. Those enzymes acting at the terminus of a polymeric substrate molecule are called exoenzymes. 

Excluded volume effects in cytoplasm, MOLECULAR CROWDING Excluding kinetic reaction mechanisms, HALDANE RELATION EXERGONIC EXOCYTOSIS EXOENZYME EXOERGIC Exo-j8-f ru ctosi d ase,... 

Trichoderma species have a powerful set of well-characterized exoenzymes involved in the cellulolytic pathway exo-/ -l,4-glucanase which hydrolyzes amorphous and microcrystalline cellulose endo-/ -l,4-glucanase... 

In common with other exoenzymes, external /3-D-fructofuranosidase is associated with much carbohydrate.90,119,127-130 Thus, the enzyme of... 

In Azotobacter vinelandii, urease appears to be synthesized only when urea or thiourea is present (75). A study of the urease constitutive in Corynebacterium renale (76) did not reveal features remarkably different from the plant enzyme. A similar conclusion was reached in the characterization of a highly purified enzyme from B. pasteurii (77). Stewart (78) has devised a medium for the detection of urease activity in pseudomonads and has resolved uncertainties that have developed in the literature. It has been reported that Sarcina ureae produces urease as an exoenzyme (79). 

Manefield M, Welch M, Givskov M, Salmond GPC, Kjelleberg S (2001) Halogenated Furanones from the Red Alga, Delisea pulchra, Inhibit Carbapenem Antibiotic Synthesis and Exoenzyme Virulence Factor Production in the Phytopathogen Erivinia carotovora. FEMS Microbiol Lett 205 131... 

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