The effect of NaCl, KCl, MgCl 2 and CaCl 2 on enzyme activity was determined. This compound is also used in electrochemical and photochemical biosensors and has antibacterial activity toward pathogenic bacteria. Thionine acetate, a planar cationic phenothiazinium dye, has been shown to bind to lysozyme. The NAG-thiazoline derivative thiamet G is a potent inhibitor of β-acetylglucosaminidases, while miglitol (Glyset) is used as a drug for treatment of type II diabetes. The alkaloid castanospermine is also a β-glucosidase inhibitor. 1-Deoxynojirimycin, a D-glucose analogue, is the best known iminosugar. Iminosugars, alkaloids and their synthetic analogues ( Figure 1) can act as glycosidase inhibitors by mimicking the glycosyloxocarbenium ion intermediate and related transition states in enzymatic glycoside hydrolysis. However, despite preventing autolysis, specific inhibition of LTs may also increase the potency of β-lactam antibiotics against bacteria, as exemplified by the action of the bulgecins. aeruginosa by Ivy was suggested to regulate the autolytic activity of lytic transglycosylases in Gram-negative bacteria that are unable to O-acetylate their peptidoglycan. Inhibition of the membrane-bound lytic transglycosylase MltB from P. Vertebrate lysozymes are also inhibited by the proteinaceous inhibitor Ivy, which is produced by certain Gram-negative bacteria. This is used to control lytic transglycosylase activity and so prevent autolysis. Many bacterial species, including human pathogens such as Bacillus anthracis, Staphylococcus aureus, Neisseria meningitides and Neisseria gonorrhoeae, inhibit the activity of both lysozyme and lytic transglycosylases by acetylation of C-6 hydroxyl moieties of NAM residues in their peptidoglycan. Unlike lysozymes, they do so by catalysing an intramolecular transglycosylation reaction that forms 1,6-anhydromuropeptides, which can be recycled to form fresh peptidoglycan but which may also act as inducers of β-lactamase production and as virulence factors. Lytic transglycosylases are important peptidoglycan-degrading glycosidases, that catalyse cleavage of the β-1,4-glycosidic bond between NAM and NAG residues. The sacculus degradation and remodelling activities are catalysed by enzymes including glycosidases, amidases, endopeptidases and carboxypeptidases. The muropeptides released from the sacculus are recycled by the cell. Escherichia coli turns over about 50% of its sacculus per generation, to allow cell growth and division, insertion of proteins into the cell wall and other processes. Peptidoglycan is composed of glycan strands of repeating N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) residues linked by β-1,4-glycosidic bonds, cross-linked via peptide side-chains. Bacterial cells are surrounded by a peptidoglycan sacculus on the outside of the cytoplasmic membrane, which is essential for maintaining cell strength and integrity.
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