Reduction enzymes proteins

A topical enzyme aids in the removal of dead soft tissues by hastening the reduction of proteins into simpler substances. This is called proteolysis or a proteolytic action. The components of certain types of wounds, namely necrotic (dead) tissues and purulent exudates (pus-containing fluid), prevent proper wound healing. Removal of this type of debris by application of a topical enzyme aids in healing. Examples of conditions that may respond to application of a topical enzyme include second- and third-degree bums, pressure ulcers, and ulcers caused by peripheral vascular disease An example of a topical enzyme is collagenase (Santyl). 

A component of the ribotide reductase complex of enzymes, protein Ba, has been shown to contain two non-heme iron atoms per mole (77). This enzyme plays a vital, albeit indirect, role in the synthesis of DNA. Curiously, the lactic acid bacteria do not employ iron for the reduction of the 2 hydroxyl group of ribonucleotides. In these organisms this role has been assumed by the cobalt-containing vitamin Bi2 coenzyme (18). The mechanism of the reaction has been studied and has been shown to procede with retention of configuration (19). 

Mammalian thioredoxin reductases are a family of selenium-containing pyridine nucleotide-disulfide oxidoreductases. These enzymes catalyze NADPH-dependent reduction of the redox protein thioredoxin (Trx), which contains a redox-active disulfide and dithiol group and by itself may function as an efficient cytosolic antioxidant [77]. One of the functions of Trx/ thioredoxin reductase system is the NADPH-catalyzed reduction of protein disulfide [78] ... 

Redox reaetions and hydrolysis are the predominant metabolie eonversions triggered by the intestinal microflora. The main reductive enzymes produeed by the intestinal mieroflora are nitroreductase, deaminase, urea dehydroxylase, and azoreduetase the hydrolytic enzymes are P-glucoronidase, P-xylosidase, P-galaetosidase, and a-L-arabinosidase. Studies conducted by Macfarlane and co-workers have shown that proteolysis ean also happen in the colon [31]. More recent findings by this group indieate that bacterial fermentation of proteins in humans could account for 17% of... 

The reduction in protein synthesis obviously has other ramifications, such as a deficiency in hepatic enzymes and a consequent general disruption of intermediary metabolism. Methylation reactions are presumably also affected. 

When the catalytic reaction of 6-hydroxymellein synthase is carried out in the absence of NADPH or with monomeric enzyme, keto-reduction of the carbonyl group of the triketomethylene chain does not take place, and the synthase liberates triacetic acid lactone instead of 6-hydroxymellein [64, 71]. However, the efficiencies of product formation are markedly lower than for the normal reaction. Two mechanisms could account for the low efficiency of triacetic acid lactone formation observed in the monomeric and the NADPH-depleted dimeric forms of 6-hydroxymellein synthase. These are 1) Reduced affinity of the cosubstrates acetyl-CoA and/or malonyl-CoA for the enzyme protein with the incomplete reaction centers 2) Reduced rate of reaction of acyl-CoA condensation and/or product liberation. To examine these possibilities, kinetic parameters of the two triacetic acid lactone-forming reactions were compared with those of the normal reaction which produces 6-hydroxymellein. The Km value of 6-hydroxymellein synthase for acetyl-CoA in the normal reaction was estimated to be 22 pM, while in both the NADPH-depleted dimer and the monomer reactions the affinity of 6-hydroxymellein synthase protein for acetyl-CoA was markedly lower at 284 and 318 pM respectively. By contrast the Km values for malonyl-CoA in the normal and the two abnormal reactions were essentially the same (40 - 43 pM), indicating that the affinity of 6-hydroxymellein... 

These are involved in a wide range of electron-transfer processes and in certain oxidation-reduction enzymes, whose function is central to such important processes as the nitrogen cycle, photosynthesis, electron transfer in mitochondria and carbon dioxide fixation. The iron-sulfur proteins display a wide range of redox potentials, from +350 mV in photosynthetic bacteria to —600 mV in chloroplasts. 

The system protecting organisms from free radical excess comprises enzymes with oxide reductive activity, non-enzyme proteins, polypeptides, water and oil-soluble vitamins, SH-containing amino acids, flavonoids, carotinoids, etc. [40], Most of these compounds prevent oxidative stress evolution by interrupting chain oxidative reactions. That is why these substances are called substances with antiradical activity as well as antioxidants (AO). Foodstuff, nutrients and some drugs are sources of most antioxidants. 

Cyclic Voltammetric Behavior of the PPy-GOD Film. Figure 1 shows the cyclic voltammetric curves of a PPy-GOD film (4000 A) in phosphate buffer solution with pH 7.4 at different scan rates. Both anodic and cathodic peaks should correspond to the redox reactions of PPy chains. The peak potentials, which were recorded at the scan rate of 200 mV/s, were -380 mV and -200 mV for cathodic and anodic peaks, respectively. This is similar to the potential shifts of the PPy film doped with large anions (27) such as poly(p-styrenesulfonate). Enzyme protein molecules are composed of amino acid and have large molecular size, which can not move out freely from the PPy-GOD film by the application of the reduction potential. In order to balance the charge of the Pfy-GOD film, cations must move into the film, and redox potentials move toward a more negative potential. This behavior is different from the one observed for the PPy-GOD film, which was prepared in the solution of GOD... 

The effects of premelanoidins on nitrogen retention is explained by a reduction in protein digestibility due to (a) the inactivation of the proteolytic enzymes, (b) the formation of indigestible peptides (20,38), (c) the inhibitory effects on amino acid absorption (33) and (d) by a decrease in the efficiency of the protein synthesis. The Maillard products also have an inhibitory effect on the intestine saccharidases (39). 

Second, GSH functions, presumably nonenzymically, in the reduction of protein thiols which have become oxidized to mixed disulfides (803). In this latter function GSH in some cases converts inactive enzymes to active ones, or vice versa, and may thus serve as a means of metabolic control. Examples of this important possibility are glycogen synthetase D (EC 2.4.1.11) and fructose-1,6-diphosphatase (EC 3.1.3.11). The D form of glycogen synthetase is dependent for activity upon the presence of glucose 6-phosphate. The enzyme is inactivated by GSSG and reactivated by GSH (204). Mixed disulfide formation between thiols of the enzyme and GSSG leads to a decrease in affinity of the enzyme for its activator (205). 

Uchida, Suzuki, and Ichihara (878) isolated a soluble enzyme system (thereby possibly excluding mitochondrial participation) from rabbit liver, and partially purified it. Two enzymes were involved. The first of these converted p-hydroxyphenylpyruvic acid to 2,5-dihydroxyphenylpyruvic acid. If this enzyme was resolved, vitamin C alone did not restore the activity, but vitamin C and vitamin B12 did. The amount of B12 required was very low, and they suggested that the true enzyme was a Bw derivative, possibly aquocobalamin hydroxide bound to enzyme protein, and that the function of the ascorbic acid was solely to stabilize the reactive form of the coenzyme. This agrees with the work of La Du and Greenberg (524), who considered the role of ascorbic acid to be quite unspecific. Ascorbate increased the rate of tyrosine oxidation in liver preparations but the net consumption was zero, and moreover numerous ene-diols were just as effective on a molar basis. La Du and Greenberg considered that ascorbic acid participates in a cyclic oxidation-reduction and happens to be a substance of the correct oxidation-reduction potential either to participate directly or to protect some other participant. 

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