Protectors, enzyme

H. Frenkel-Mullerad and D. Avnir, Sol-gel materials as efficient enzyme protectors preserving the activity of phosphatases under extreme pH conditions. J. Am. Chem. Soc. 127, 8077-8081 (2005). 

The popular acids for deprotection by acidolysis are hydrogen fluoride for benzyl-based protectors and trifluoroacetic acid for rerr-butyl-based protectors. The use of hydrogen fluoride for deprotection emerged from the observation that it is a good solvent for dissolving enzymes (because of the N-to-0 acyl shift see Section 6.6), and that the enzymatic activity is recovered (O-to-N acyl shift) in saline solution. Two different approaches are employed for removal of benzyl-based... 

Irradiation of commercial shrimp in which melanogenesis had begun accelerated the reaction. It was postulated that the quinone-like end products of the reaction sequence acted as competitive inhibitors for the reaction and also functioned as radiation protectors for the enzyme. Subsequent irradiation would destroy the capacity of the end products to inhibit the reaction and simultaneously preserve the enzyme activity, thus accelerating further melanogenesis. 

Evidence for the activity of some radioprotectors as inhibitors of free radical processes has appeared, and the subject has been reviewed Involvement of MEA as well as of metal ionsf in free radical formation in proteins and bacteria has been observed. It was also found that cysteine and glutathione could accept electrons from irradiated proteins, whereas cystine and non-sulfur compounds did not Presence of metal ions, particularly cupric, had a protective effect for ribo-nuclease, presumably by intercepting electrons and preventing radical formation on the enzymer A protective effect of mucopolysaccharide polyanions and cysteine for trypsin and RHA, however, was not considered to be due to transfer of radiation energy to the protectors " Furthermore, substances known to react with H atoms or the aqueous electron did not protect hydrated E. coll cells from X-rays ... 

Incubation of luciferase with the not reduced activated FMN derivative results in irreversible inactivation of the enzyme. The activated FMN derivative, obviously, modifies no more one functional groups of luciferase, because the coefficient characterizing a number of modified protein residues was determined as 1.05. The addition in an incubation mixture the second substrate of luciferase - tetradecanal before adding the activated FMN derivative, does not protect the luciferase from inactivation. The addition of the protector,of SH-groups - DTT result in essential inhibition decreasing. The activated FMN derivative reacts most likely with SH-groups of luciferases, which, as is known, are good nucleophile. "... 

The (HSO3)" inhibitor is a protector of the enzyme against cya-nolysis and a 1 1 complex of the inhibitor and the enzyme has been isolated. The proposed mode of interaction involves the Mo=8 group directly (Fig. 36). The suggestion that the interaction product very... 

Thus, after 24 hours, 5 g. of urea are destroyed in the presence of sugar, while the control test shows a disappearance of only 1.96 g. The sugar thus acts as protector of the enzyme... 

We produce free radicals every single day. They re part of living, and we do have natural protectors floating around. Specialized enzymes in our white blood cells, vitamins C and E, and other dietary antioxidants (free radical scavengers ), are examples. With insufficient defenses, some radicals get away and cause cellular damage. 

Kim K, Kim IH, Lee KY et aL The isolation and purification of a specific protector protein which inhibits enzyme inactivation by a thiol/Fe(III)/02 mixed-function oxidation system. J Biol Chem 1988 263 4704-4711. 

Ascorbate and ascorbate-related enzyme levels depend on the developmental stage of plants (Cakmak et al., 1993 Luwe et al., 1993 Esaka et al., 1992). In general, the significance of changes in the ascorbate system in plants seems to be related to its functions as a protector against oxidative stress and/or as a regulating agent of proliferation, differentiation, and maturation events in plants. 

N-Acetyl-l-cysteine (NAC), another significant precursor of the GSH biosynthesis, has broadly been used as effective antioxidant in a form of nutritional supplement (Soloveva M. E et al 2007, Thibodeau P. A., et al 2001). At low concentrations, it is a powerful protector of a-l-antiproteinase against the enzyme inactivation by HOCl. NAC reacts with HO radicals and slowly with H O however, no reaction of this endobiotics with superoxide anion radical was detected [88]. 

Fig. 2. Distribution of radioactivity covalently attached to (Na + K ) adenosine triphosphatase that has been photolyzed in the presence of [ ClCM-cymarin. Samples of enzyme that had been photolyzed either in the presence of the complete MgATP phosphorylating system (O) or the complete system plus a 25-fold excess of cymarin as protector ( ) were run on sodium dodecyl sulfate gels which were scanned, sliced, and counted. The A2M trace from the gel with the unprotected sample was divided into segments exactly as the gel had been sliced. The mean of each of these segments was calculated, and the values were plotted ( ). The units of are arbitrary since the scanner was uncalibrated. The three protein components are (a) cross-linked /3 dimer (b) large chain (c) small chain.

The formation of PPy on an electrode surface provides a nanoporous matrix that is highly used for the immobilization of biomolecules to design various biosensors (electrochemical biosensor, immunosensor, and DNA sensor). It also acts as a mediator to transfer the analytical signal generated by some redox enzymes to the transducer even if the redox center is deeply buried in the protein globule. In addition, it is an efficient protector of electrodes against interfacing materials (proteins present in real samples such as blood and urine). 

J.D. (2002) Reagendess pH-based biosensing using a fluorescendy-labelled dextran co-entrapped with a hydrolytic enzyme in sol-gel derived nanocomposite films. Anal. Chim. Acta, 4S17,47 59 (i) Frenkel-Mullerad, H. and Avnir, D. (2005) Sol-gel materials as efficient enzyme protectors preserving the activity of phosphatases under extreme pH conditions. /. Am. Chem. Soc., 127 (22), 8077-8081 (j) Frenkel-Mullerad, H.,... 

Sensitivity to Activators.—Many enzymes are powerfully affected by specific ions or simple solutes, which either accelerate or inhibit the reaction. Activators are divided provisionally into promoters, that increase the rate at which the reaction starts and protectors, that prolong the rate by retarding the spontaneous inactivation of the enzyme. 

Protectors.-—Agents capable of neutralising toxic contaminants or by-products during zymolysis. Thus, a-amino acids activate urease, arginase and probably other enzymes. 

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