Hydrolysis thermal inactivation

The thermal inactivation assays of soluble YLL and immobilized preparations on octyl-agarose, octadecyl epabeads and MANAE agarose were carried out incubating the same amount of lipase in three different buffers at 45°C 25 mM sodium acetate pH 5, 25 mM sodium phosphate pH 7 and 25 mM sodium carbonate pH 9. Periodically, residual enzyme activity was estimated by hydrolysis of pNPB. Soluble enzyme was submitted to the same conditions. 

From an analytical perspective, the single most important physicochemical characteristic of riboflavin is its photosensitivity (80-82). Exposure of this vitamin to ultraviolet and visible light results in irreversible photoreduction to lumiflavin and lumichrome and loss of vitamin activity. In addition, the coenzymes are subject to hydrolysis by endogenous phosphatases that are present in a number of foods. Since these enzymes are generally inactivated by thermal processing, they are a concern only in the analysis of fresh products. 

The present study indicates that the extracellular enzyme, pepsin, exhibits striking differences from its mammalian homologue with respect to optimum pH, Ea for catalysis, thermal stability, and substrate affinity. These data are interesting from the viewpoint of biological adaption at low temperatures, but they also provide some substance to our contention that enzymes from fish plant wastes can have sufficiently unique properties to justify their use over conventional sources of enzymes used as food-processing aids. The relatively low Eas for protein hydrolysis by fish pepsins indicate they may be especially useful for protein modifications at low temperatures. Alternatively, the poor thermal stability of the fish pepsins studied indicate that the enzymes can be inactivated by relatively mild blanching temperatures. The reality of this concept will have to await studies where the pepsins are used as food-processing aids. Such studies are currently underway in our laboratory. 

The kinetics of the hydroxide ion-catalyzed epimerization of pilocarpine to isopilocarpine and of its hydrolysis to pilocarpic acid have been studied (56). Both forms of degradation lead to loss of pharmacological activity. The importance of possible inactivation by epimerization during thermal sterilization of ophthalmic preparations of pilocarpine was pointed out. It was also considered that some epimerization would always occur during the extraction of pilocarpine from Jaborandi leaves, and that isopilocarpine might, therefore, be an artifact and not a genuine plant alkaloid (55). 

Catalytic Activity for Hydrolysis of p-Nitrophenyl Acetate and Heat Inactivation of Various Thermal Poly-a-Amino Adds°- ... 

Invertase proved to be a true catalyst, as it was not destroyed in the reaction and it was stUl active after catalyzing the hydrolysis of 100,000 times its weight of sucrose. The thermal stabihty of the enzyme was much greater in the presence of its substrate, sucrose, than in its absence this striking fact indicated that the invertase enters into combination with the sugar, which protects the enz5mie from inactivation. 

G. Maltodextrin F. malto-dextrines M. are concentrated aqueous solutions of nutritive saccharides, or their dehydrated products, obtained by controlled - hydrolysis of starch and having a DE-value of <20%. [QHioOsln. They are mixtures of - malto-oligosaccharides as well as of - starch polysaccharides with reduced m.w. The ->AGU are linked together by a-1,4- and a-1,6-glucosidic bonds. Production by hydrolysis is performed primarily by the action of thermally stable a-amylases from bacteria on ->com, - wheat, - waxy com, - potato or starches from - cassava, followed by inactivation of the enzyme, purification, concentration and spray-drying. 

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