Bacteria catalytic properties

MGL catalyzes the o ,7-elimination reaction of methionine to a-ketobutyrate, methanethiol, and ammonia. MGL has been isolated from a number of bacteria, including Pseudomonas putida, Aeromonas sp., Clostridium sporogenes, P. taetrolens, and Brevibacterium linens, from the primitive protozoa Entamoeba histolytica and Trichomonas vaginalis, but is not believed to be present in yeast, plants, or mammals. " " Two MGL isoforms have been isolated from T. vaginali and Entamoeba histolytica, which differ in substrate specificity, overall charge, and catalytic properties. They show a high degree of sequence identity to MGL from Pseudomonas putida. MGL has demonstrated antitumor efficacy in a number of methionine-dependent cancer cell lines. ... 

The Linhardt laboratory prepares polysaccharide lyases from Flavobacterium heparinum and Bacteroides stearcoris. These enzymes have been purified to homogeneity, cloned, and expressed in bacteria. Their physical and catalytic properties and specificity have been extensively investigated. ... 

The catalytic domains of human 25 kDa hThTPase and CyaB-like adenylyl cyclase from Aeromonas hydrophilia define a novel superfamily of domains that should bind organic phosphates (Iyer and Aravind 2002). This superfamily of proteins was therefore called CYTH (CYaB-THiamin triphosphatase), and the presence of orthologs was demonstrated in all three superkingdoms of life. This suggested that CYTH is an ancient enzymatic domain and that a representative must have been present in the last universal common ancestor (LUCA) of all extant life forms. It appears that the CYTH superfamily includes enzymes with various catalytic properties (adenylyl cyclase or inorganic triphosphatase in some bacteria, RNA triphosphatase in yeast, ThTPase in animals) but with important common features ... 

It thus appears that the mutant PRPP synthetase enzyme is structurally altered in such a way that only its regulatory properties but not its catalytic properties are affected. This selective alteration proves that these two properties are located at different sites, the enzyme being allosteric. Examples are known of mutations in bacteria (18,19) and Ehrlich ascites cells (20) which altered the susceptibility of regulatory enzymes to effector mulecules. An indication for such a mutation in man has been obtained by Henderson et al in studies on fibroblasts from two patients with purine overproduction and gout, showing reduced effectiv-ness of product inhibition of purine biosynthesis (2l). 

In fact, during the last 20 years, biosensors were successfully applied in many fields of the environmental analysis, especially due to a variety of enzymes produced by bacteria, plants, or animals. Another reason is their catalytic property and the possibility of modifying the substrate specificity through genetic engineering. 

We have chosen to explore enzymes in themK)philic anaerobic bacteria, because these kinds of microorganisms were believed to have been the first forms of life on earth and have evolved under energy limited conditions that place stress on selection of enzymes with high catalytic efficiency (2). Thermoanaerobes contain a diverse array of enzymes with unique properties and their enzyme outfits now serve as models for understanding the biodegradation of polymers such as cellulose (5). 

Lecithin has some catalytic or cocatalytic effects in multiphase systems because of its surface-active properties. Lecithin is reported to be useful as an emulsifier in the curing of aqueous dispersions of unsaturated polyesters (337). The products are more easily removed from their molds and have improved mechanical properties when lecithin is used. In a fermentation application, 1.5% soybean lecithin acts as an inducer in the preparation of cholesterol esterase using a strain of Pseudomonas bacteria (338). Aside from its role as a catalyst, initiator, or modifier, lecithin may have ancillary uses in catalyst systems as part of a protective coating (339). 

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