Resynthesis protein

The DCL was created under standard disulfide exchange conditions at pH 7.5. After equilibration for 48 hours, each of the expected 15 disulfide products could be observed in the library using LC-MS analysis (Fig. 2.11). The library was then equilibrated in the presence of CaM, followed by a centrifugation filtration step to separate protein/bound components from free components in solution. Analysis of the filtrate was complicated by the filtration membrane affecting the composition of the library. The bound components, however, provided meaningful results. Denaturation and filtration afforded a mixture of all peptides that had bound to CaM in the course of the DCL. HPLC analysis indicated significant amplification of dimer cc (80%) and a small amplification of dimer ec (10%). Resynthesis of these two components and binding assay established values of 10 and... 

The plastein reaction usually involves two steps hydrolysis of protein and resynthesis of peptide links. Yamashita et al. (20) found similar BV, digestibility, and weight gain for denatured soy meal and soy plastein. This same group (49,50) had described a one-step process by which amino acids may 5 enzymatically incorporated in intact protein to improve protein quality. With soy protein they applied a racemic mixture of D,L-methionine ethyl ester and were able to enzymatically incorporate L-methionine. As Schwimmer (51) has pointed out, one expects the methionine so incorporated to be highly available due to its location at the end of the polypeptide chains. 

Figure 5. Scheme for removing impurities from protein substrate by hydrolysis, purification, and resynthesis via the plastein reaction (i)... 

Finally, the peroxynitrite formed from the RNS and ROS can cause single-strand breaks in DNA, and this activates PARP, which transfers ADP-ribose from NAD+ to nuclear proteins. This consumes NAD+, which means that NADH levels are compromised, and hence ATP is again affected. The resynthesis of NAD+ also consumes more ATP. 

Rate of turnover In healthy adults, the total amount of protein in the body remains constant, because the rate of protein synthesis is just sufficient to replace the protein that is degraded. This process, called protein turnover, leads to the hydrolysis and resynthesis of 300 to 400 g of body protein each day. The rate of protein turnover varies widely for individual proteins. Short-lived proteins (for example, many regulatory proteins and misfolded proteins) are rapidly degraded, having half-lives measured in rrh-utes or hours. Long-lived proteins, with half-lives of days to weeks, constitute the majority of proteins in the cell. Structural proteins, such as collagen, are metabolically stable, and hare half-lives measured in months or years. 

The 3 -terminal group of three nucleotides, CCA, is invariant among all tRNA molecules and is labile, undergoing active removal and resynthesis. The rate of this turnover is sufficient to involve about 20% of the tRNA molecules of a cell per generation, but it is very much slower than the rate of participation of the tRNA molecules in protein synthesis. The physiological significance of end turnover is unknown.233 While this CCA sequence is encoded in bacterial tRNA genes, it is added in a separate reaction in eukaryotes.234... 

Waldstein, E.A., E-H. Cao, and R.B. Setlow. Adaptive resynthesis of 06-methylguanine-accepting protein can explain the differences between mammalian cells proficient and deficient in methyl excision repair. 

The neuroprotective properties of mild hypothermia have been demonstrated in numerous experimental animal models. Research in this area has been conducted for many years, yet the mechanisms of cerebral protection by mild hypothermia remain unclear and continue to be the subject of intense investigation. The neuroprotective effects of mild hypothermia have been attributed to alterations in metabolic rate (24), neurotransmitter release (25-27), activity of protein kinases (28), resynthesis of cellular repair proteins (29), cerebral blood flow (30), preservation of the blood-brain barrier (BBB) (31), attenuation of inflammatory processes (32,33), and decreases in free radical production (34). Although these may all be components of a complex cascade leading to neurologic injury, it has become increasingly clear that the primary mechanism of action of hypothermia may be different at various temperatures as well as under different ischemic and traumatic conditions. 

Although research in this area has been conducted for more than 40 yr, the mechanisms of cerebral protection by mild hypothermia remain unclear and are still a source of controversy. Proposed mechanisms of neuroprotection by mild hypothermia include suppression of neurotransmitter release (2,3), reduced free radical production (4), activity of protein kinases (5), resynthesis of cellular repair proteins (6),... 

A function of ovotransferrin in the avian egg has not been demonstrated. As attractive as is the concept of a function for transferrin during embryonic development, essentially all the iron of the egg is in the yolk and during embryonic development the main fate of the egg white appears to be as a source of food for the embryo (61). However, there is so very little known about the breakdown and resynthesis of protein and other substances during embryo development in the avian egg, the iron binding property of the transferrin might have a yet unrecognized function. 

Plastein Formation. Plastein formation is another example of using proteases to modify high-protein food systems to drastically change the properties of that system (II). In the plastein reaction a protease such as papain is used to partially hydrolyze the proteins to about a 10,000-20,000-dalton size at a pH near neutrality. After concentrating the hydrolyzate to 35% (based on protein) and a change in pH, the same protease or a different one is used to catalyze the resynthesis of a few peptide bonds. This may result in a decrease in the solubility of the protein. 

More details of the plastein reaction and its application to remove pigments such as chlorophyll, or to remove off-flavor components such as the beany taste of soybeans, are shown in Figure 2. The protein of the food system is solubilized and denatured (in order to achieve proteolysis), a protease is added, and the hydrolytic reaction is allowed to proceed. On partial hydrolysis of the protein the pigments and flavor constituents are released from the protein they are removed, the hydrolyzate is concentrated, and resynthesis and/or rearrangement of the amino acid sequence of the polypeptides is catalyzed by the same or a different protease. Resynthesis also can be carried out in the presence of added amino acid esters in order to improve the nutritional/functional properties of the protein. 

Figure 2. A process of enzymatic protein degradation and resynthesis for producing a plastein with improved acceptability and an improved amino acid composition (11)...

Endopeptidases. Our expanding understanding of the relationship between structure and functionality of food proteins presents the opportunity for designing functionality into proteins by selective, specific proteolytic modification. Control of reaction and prevention of autolysis offered by immobilization are essential to establish the conditions for a highly selective modification. Hydrolysis at specific positions in the primary structure of proteins could be coupled with resynthesis of peptide bonds by selection of conditions, for example, as in the plastein reaction. By careful choice of enzymes and conditions according to the characteristics of the substrate proteins, it may be possible to design new structures from known food proteins. 

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