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An enzyme which causes bacterial cell walls to crumble. The lysozyme disrupts the walls by catalysing the hydrolysis of the polysaccharides which comprise them. So, if you ask a coli, this is an evil enzyme. If you ask me, I have to say it´s of great use in the lab.

This enzyme catalyzes the hydrolytic cleavage of the cell walls of eubacteria.

It does so by cleaving the glycosidic beta(1-4) linkages of the NAM-NAG polymer. This is a repeating polymer of N-acetylmuramic acid and N-acetyl glucosamine. It also has the ability to cleave poly NAG chains.

Its catalytic mechanism involves two important amino acid residues. These are Glutamic Acid 35 and Aspartic Acid 52. At the physiological pH Glu35 is protonated and Asp52 remains unprotonated.

The steps of the reaction are:

1) Lysozyme binds the substrate. Steric interactions cause the distortion of the subunit located at the D position of the enzyme to assume the half-chair conformation.

2) Glu35 acts as a general acid catalyst by partially donating the carbonyl H of its side chain to the O atom of the glycosidic linkage. This cleaves the linkage.

3) This cleavage creates a positively charged planar oxonium ion. This relieves the strain of the half-chair conformation. Asp52 electrostatically stabilizes the positive oxonium ion.

4) Glu35 then acts as a general acid by abstracting a proton from water. This primes the hydroxyl for nucleophilic attack on the C1 of the D ring. The resultant OH group is in the Beta configuration.

A protein enzyme found in saliva and tears that dissolves the cell walls of bacteria.


From the BioTech Dictionary at http://biotech.icmb.utexas.edu/. For further information see the BioTech homenode.

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