Degradation, proteolytic

Although the mechanisms involved are not yet fully understood, one elimination process of IgG as proteins is a slow proteolytic degradation this takes place predominantly in hepatic and reticuloendothelial cells. 

A number of different molecular mechanisms can underpin the loss of biological activity of any protein. These include both covalent and non-covalent modification of the protein molecule, as summarized in Table 3.20. Protein denaturation, for example, entails a partial or complete alteration of the protein s 3-D shape. This is underlined by the disruption of the intramolecular forces that stabilize a protein s native conformation, viz hydrogen bonding, ionic attractions and hydrophobic interactions. Covalent modifications of protein structure that can adversely effect its biological activity are summarized below. 

Proteolytic degradation of a protein is characterized by hydrolysis of one or more peptide (amide) bonds in the protein backbone, generally resulting in loss of biological activity. Hydrolysis is usually promoted by the presence of trace quantities of proteolytic enzymes, but can also be caused by some chemical influences. 

Proteins differ greatly in their intrinsic susceptibility to proteolytic attack. Resistance to proteolysis seems to be dependent upon higher levels of protein structure (i.e. secondary and tertiary structure), as tight packing often shields susceptible peptide bonds from attack. Denaturation thus renders proteins very susceptible to proteolytic degradation. 

A number of strategies may be adopted in order to minimize the likelihood of proteolytic degradation of the protein product, these include  

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Protein G. This vitamin K-dependent glycoproteia serine protease zymogen is produced ia the Hver. It is an anticoagulant with species specificity (19—21). Proteia C is activated to Proteia by thrombomodulin, a proteia that resides on the surface of endothefial cells, plus thrombin ia the presence of calcium. In its active form, Proteia selectively iaactivates, by proteolytic degradation. Factors V, Va, VIII, and Villa. In this reaction the efficiency of Proteia is enhanced by complex formation with free Proteia S. la additioa, Proteia activates tissue plasminogen activator, which... 

Lowey, S., Goldstein, L., Cohen, C., Luck, S.M. (1966). Proteolytic degradation of myosin and the meromyosins by a water-insoluble polyanionic derivative of trypsin. J. Mol. Biol. 23,287-304. 

Research activity in this area has mainly concentrated on the design and in vitro studies of amphiphihc helical /9-peptides with antimicrobial activity. In view of their high propensity for helical conformations as well as their resistance to proteolytic degradation, /9-peptides represent promising antibacterial candidates. 

The coupling of hirudin to polyethylene glycol (PEG) increases its half-life. PEG-hirudin is also less susceptible to proteolytic degradation (60). 

Poduslo JF, Curran GL, Kumar A, Frangione B, Soto C. Beta-sheet breaker peptide inhibitor of Alzheimer s amyloidogenesis with increased blood-brain barrier permeability and resistance to proteolytic degradation in plasma. J Neurobiol 1999 39 371-382. 

The results for bacterial whole-cell analysis described here establish the utility of MALDI-FTMS for mass spectral analysis of whole-cell bacteria and (potentially) more complex single-celled organisms. The use of MALDI-measured accurate mass values combined with mass defect plots is rapid, accurate, and simpler in sample preparation then conventional liquid chromatographic methods for bacterial lipid analysis. Intact cell MALDI-FTMS bacterial lipid characterization complements the use of proteomics profiling by mass spectrometry because it relies on accurate mass measurements of chemical species that are not subject to posttranslational modification or proteolytic degradation. 

P. fluorescens has well-developed mechanisms for the secretion of proteins into the periplasm which facilitates S—S bond formation and proper N-terminal processing. It also allows one to reduce the formation of inclusion bodies and, thus, the additional costs caused by refolding processes. Proteolytic degradation of the expressed protein is also low, and very high... 

Lukacin, R., Groning, I., Schiltz, E., Britsch, L. and Matem, U. (2000). Purification of recombinant flavanone 3 beta-hydroxylase from Petunia hybrida and assignment of the primary site of proteolytic degradation. Archives of Biochemistry and Biophysics 375 364-370. 

In the quest to find other plants that are suitable as bioreactors, various monocoty-ledonous and dicotyledonous species have been tested. These include corn [16], rice and wheat [17], alfalfa [18], potato [19, 20], oilseed rape [21], pea [22], tomato [23] and soybean [24]. The major advantage of cereal crops is that recombinant proteins can be directed to accumulate in seeds, which are evolutionar specialized for storage and thus protect proteins from proteolytic degradation. Recombinant proteins are reported to remain stable in seeds for up to five months at room temperature [17] and for at least three years at refrigerator temperature without significant loss of activity [25]. In addition, the seed proteome is less complex than the leaf proteome, which makes purification quicker and more economical [26]. 

In order to make molecular farming commercially profitable, recombinant proteins must be produced at a sufficiently high yield and in an active form. It has become clear that, for high-level protein accumulation, the stability of transgene expression can be as important as the expression level itself. The quantity of protein is determined by the rate of protein synthesis, assembly as well as proteolytic degradation [83]. 

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