Lysis cell wall

IB 90,000 250 (8) transglycosylase, major transpeptidase of cell elongation essential for cylindrical cell wall synthesis rapid lysis... 

Chemical lysis, or solubilization of the cell wall, is typically carried out using detergents such as Triton X-100, or the chaotropes urea, and guanidine hydrochloride. This approach does have the disadvantage that it can lead to some denaturation or degradation of the produci. While favored for laboratory cell disruption, these methods are not typically used at the larger scales. Enzymatic destruction of the cell walls is also possible, and as more economical routes to the development of appropriate enzymes are developed, this approach could find industrial application. Again, the removal of these additives is an issue. 

Several drugs in current medical use are mechanism-based enzyme inactivators. Eor example, the antibiotic penicillin exerts its effects by covalently reacting with an essential serine residue in the active site of glycoprotein peptidase, an enzyme that acts to cross-link the peptidoglycan chains during synthesis of bacterial cell walls (Eigure 14.17). Once cell wall synthesis is blocked, the bacterial cells are very susceptible to rupture by osmotic lysis, and bacterial growth is halted. 

Lysozyme is an enzyme that hydrolyzes polysaccharide chains. It ruptures certain bacterial cells by cleaving the polysaccharide chains that make up their cell wall. Lysozyme is found in many body fluids, but the most thoroughly studied form is from hen egg whites. The Russian scientist P. Laschtchenko first described the bacteriolytic properties of hen egg white lysozyme in 1909. In 1922, Alexander Fleming, the London bacteriologist who later discovered penicillin, gave the name lysozyme to the agent in mucus and tears that destroyed certain bacteria, because it was an enzyme that caused bacterial lysis. 

Penicillin has an interesting mode of action it prevents the cross-linking of small peptide chains in peptidoglycan, the main cell wall polymer of bacteria. Pre-existing cells are unaffected, but all newly produced cells are abnormally grown. The newborn cells are unable to maintain their wall rigidity, and they are susceptible to osmotic lysis. 

This structure is the traditional target for a group of antibiotics which include the penicillins (Chapter 5), but a httle-noticed report which appeared in 1948 showed that low concentrations of disinfectant snbstances cansed cell wall lysis such that a normally tuibid suspension of bacteria became clear. It was thought that these low concentrations of disinfectant cause en mes whose normal role is to synthesize the cell wall to reverse their role in some way and effect its dismption or lysis. 

IV. PARASITISM. Lysis by hydrolytic enzymes excreted by microorganisms is a well-known feature of mycoparasitism. Chitinase and P-l,3 glucanase (laminarase) are particularly important enzymes secreted by fungal mycoparasites capable of degrading the fungal cell wall components, chitin, and P-1,3 glucan (131-134). 

Protoplasmic structures are not very stable. Consequently, if protective agents were not employed, destruction of the walls was accompanied by a rapid lysis of the protoplasts, followed by the liberation of most of the cell protein and nucleic acid in soluble form. This could be prevented by employment of the enzyme in a 0.2 M solution of sucrose or cane sugar. After digestion of the cell walls, the living protoplasts rounded up into spheres. 

Thus, investigation of the kinetics of lysozyme-catalyzed lysis of bacterial cell walls has shown that the presence of an organic solvent decreased the overall reaction rate reversibly with the rados of the maximum rate constant of lysis in water and in mixed solvent given by... 

In one case, a small peptide with enzyme-like capability has been claimed. On the basis of model building and conformation studies, the peptide Glu-Phe-Ala-Ala-Glu-Glu-Phe-Ala-Ser-Phe was synthesized in the hope that the carboxyl groups in the center of the model would act like the carboxyl groups in lysozyme 17). The kinetic data in this article come from assays of cell wall lysis of M. lysodeikticus, chitin hydrolysis, and dextran hydrolysis. All of these assays are turbidimetric. Although details of the assay procedures were not given, the final equilibrium positions are apparently different for the reaction catalyzed by lysozyme and the reaction catalyzed by the decapeptide. Similar peptide models for proteases were made on the basis of empirical rules for predicting polypeptide conformations. These materials had no amidase activity and esterase activity only slightly better than that of histidine 59, 60). 

Table L Synergism between Glucanases in C wriffis lysis (SCL) and Solubilization of Cell Wall Glucans (SCS)...

Table IV. Effect of Sequential Addition of Glucanases on the Lysis and Solubilization of C utilis Cell Wall Glucan...

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