Enzymatic cleavage, of proteins

The selective enzymatic cleavage of proteins is critical to many biological processes. For example, the clotting of blood depends on the enzyme thrombin cleaving fibrinogen at specific points to produce fibrin, the protein that forms a clot. 

Peptide masses that do not immediately match theoretical masses in the identification process, can not only be the result of a post-translational modification, but may arise during the processing of the sample. A tool that can identify possible peptides that have resulted from non-specific chemical or enzymatic cleavage of proteins is the FindPept tool (http //www.expasy.ch/tools/). 

Hapten density, and also the common positions where haptens are bound, can also be estimated by cyanogen bromide or enzymatic cleavage of the protein and either MALDI-MS or separation of the components by reversed-phase ion-pair chromatography and electrospray or electrospray time-of-flight (TOF) analysis. 

Water is not just the solvent in which the chemical reactions of living cells occur it is very often a direct participant in those reactions. The formation of ATP from ADP and inorganic phosphate is an example of a condensation reaction in which the elements of water are eliminated (Fig. 2-22a). The reverse of this reaction— cleavage accompanied by the addition of the elements of water—is a hydrolysis reaction. Hydrolysis reactions are also responsible for the enzymatic depolymerization of proteins, carbohydrates, and nucleic acids. Hydrolysis reactions, catalyzed by enzymes called... 

Fibrin polymerization is initiated by the enzymatic cleavage of the fibrinopeptides, converting fibrinogen to fibrin monomer (Fig. 1). Then, several nonenzymatic reactions yield an orderly sequence of macromolec-ular assembly steps. Several other plasma proteins bind specifically to the resulting fibrin network. The clot is stabilized by covalent ligation or crosslinking of specific amino acids by a transglutaminase, Factor XHIa. 

The small intestine continues the chemical digestion process started in the stomach with a focus on enzymatic cleavage of fats and sugars. Proteins, already partially broken down in the stomach, are cleaved into individual amino acids. Once different food types have been digested completely, they are ready for absorption. The small intestine consists of three regions duodenum, jejunum, and ileum (Table 3.5).5... 

Houthaeve, T. Gausepohl, H. Mann, M. Ashman, K. 1995. Automation of micro-preparation and enzymatic cleavage of gel electrophoretically separated proteins. FEBS Lett., 376,91-94. 

Tuftsin 58, isolated from the protein leukokinin in 1970 by Najjar et al.141) by enzymatic cleavage of a y-globulin fraction, stimulates phagocytosis. 

---