Protease modification

This data, together with the observation of prolific protease activity in crude commercial cullulase preparations that are probably obtained from older cultures, has led us to speculate that the multiple enzyme peaks in the older cultures could have resulted from protease modification of one parent endoglucanase. This prompted us to discontinue the use of commercial cellulase preparations. 

Proteases modification of protein fibers (wool), improvement of felting properties, improvement of printability of wool, degumming of silk... 

Peptide labeled with fluorescein and coumarin is quenched until cleavage by protease, modification by phosphorylation, or dephosphorylation by kinase or phosphatase produces resistance to proteolytic cleavage... 

Two other practical appHcations of en2yme technology used in dairy industry are the modification of proteins with proteases to reduce possible allergens in cow milk products fed to infants, and the hydrolysis of milk with Hpases for the development of Hpolytic flavors in speciaHty cheeses. 

Modification by SUMO is a reversible and often highly dynamic process. Cleavage of the isopeptide bond between SUMO and its targets is accomplished by SUMO specific cysteine proteases of the Ulp/SENP family (Fig. 2). Six members were identified in humans,... 

A number of iron-containing, ascorbate-requiring hydroxylases share a common reaction mechanism in which hydroxylation of the substrate is linked to decarboxylation of a-ketoglutarate (Figure 28-11). Many of these enzymes are involved in the modification of precursor proteins. Proline and lysine hydroxylases are required for the postsynthetic modification of procollagen to collagen, and prohne hydroxylase is also required in formation of osteocalcin and the Clq component of complement. Aspartate P-hydroxylase is required for the postsynthetic modification of the precursor of protein C, the vitamin K-dependent protease which hydrolyzes activated factor V in the blood clotting cascade. TrimethyUysine and y-butyrobetaine hydroxylases are required for the synthesis of carnitine. 

Blake, 1989 Winyard et al., 1989). We suggest that within the inflamed rheumatoid joint (or the artery wall in atherogenesis), the production of ROM and proteases by endothelial cells and/or macrophages may cause the release of copper ions from Cp (see Section 2.2.3.2). It has been reported that Cp is cleaved faster in serum from patients with inflammatory diseases when compared to normal serum (Laurell, 1985). The oxidative modification of LDL by Cp-derived copper ions may explain the observation that increased serum cholesterol values are associated with accelerated atherosclerotic progression in men with high serum copper concentrations (Salonen et al., 1991). 

The starting point for much of the work described in this article is the idea that quinone methides (QMs) are the electrophilic species that are generated from ortho-hydro-xybenzyl halides during the relatively selective modification of tryptophan residues in proteins. Therefore, a series of suicide substrates (a subtype of mechanism-based inhibitors) that produce quinone or quinonimine methides (QIMs) have been designed to inhibit enzymes. The concept of mechanism-based inhibitors was very appealing and has been widely applied. The present review will be focused on the inhibition of mammalian serine proteases and bacterial serine (3-lactamases by suicide inhibitors. These very different classes of enzymes have however an analogous step in their catalytic mechanism, the formation of an acyl-enzyme intermediate. Several studies have examined the possible use of quinone or quinonimine methides as the latent... 

B. brevis is not so well studied. It also shows low extracellular protease activity, and a protease-deficient strain is available [43]. High [44] and low [45] copy number plasmids are constructed for different levels of expression. Modification of signal sequences can enhance yields of eukaryotic proteins [46]. The yields can be up to 3 gL-1 media. 

Cervera and Levine [81] studied the mechanism of oxidative modification of glutamine synthetase from Escherichia coli. It was found that active oxygen species initially caused inactivation of the enzyme and generated a more hydrophilic protein, which still was not a substrate for the protease. Continuous action of oxygen species resulted in the formation of oxidized protein subjected to the proteolytic attack of protease. 

Soya Proteins. Early attempts to make albumen substitutes from soya protein also ran into problems. A bean flavour tended to appear in the finished product. A solution to these problems has been found. Whipping agents based on enzyme modified soy proteins are now available. The advantage of enzymatic modification is that by appropriate choice of enzymes the protein can be modified in a very controlled way. Chemical treatment would be far less specific. In making these materials the manufacturer has control of the substrate and the enzyme, allowing the final product to be almost made to order. The substrates used are oil-free soy flakes or flour or soy protein concentrate or isolate. The enzymes to use are chosen from a combination of pepsin, papain, ficin, trypsin or bacterial proteases. The substrate will be treated with one or more enzymes under carefully controlled conditions. The finished product is then spray dried. 

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