Lysozyme EC

Lysozyme (muramidase, mucopeptide iV-acetylmuramylhydrolase) is a widely distributed enzyme which lyses certain bacteria by hydrolysing the (l-4)-linkage between muramic acid and N-acetylglucosamine of mucopolysaccharides of the bacterial cell wall. 

Lysozyme was isolated from human milk in 1961 by Jolles and Jolles, who believed that bovine milk was devoid of lysozyme. Milks of many species have since been shown to contain lysozyme and several have been isolated and characterized. Human and equine milks are an exceptionally rich source, containing 130mgl (3000 times the level of bovine milk) and about 800mgl S respectively (see Farkye, 1992). 

The pH optima of human milk lysozyme (HML), bovine milk lysozyme (BML) and egg-white lysozyme (EWL) are 7.9, 6.35 and 6.2, respectively. BML has a molecular weight of 18kDa compared with 15kDa for HML and EWL. The amino acid composition of BML is reported to be considerably different from that of HML or EWL. All lysozymes are relatively stable to heat at acid pH values (3-4) but are relatively labile at pH greater than 7. Low concentrations of reducing agents increase the activity of BML and HML by about 330%. 

No beneficial effects from lysozyme on the shelf-life of milk have been reported. Addition of lysozyme to milk reduces its heat stability but the level 

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Related enzymes are N-acetylglucosaminidases, EC 3.2.1.30, some of which can act to hydrolyse the terminal, non-reducing iV-acetylglucosamine residue of chitin and lysozymes, EC 3.2.1.17, some of which can act slowly as endohydrolases. 

This enzyme [EC 3.2.1.14] (also referred to as chitodex-trinase, l,4-j8-poly-A-acetylglucosaminidase, and poly-j8-glucosaminidase) catalyzes the hydrolysis of the l,4-j8-linkages of A-acetyl-D-glucosamine polymers of chitin. It should be noted that some chitinases will also display the activity observed with lysozyme [EC 3.2.1.17]. 

An even more serious disadvantage of this technique is that it often impairs the biological activity of the modified protein. The activities of hen s egg lysozyme (EC 3.2.1.17) and alpha amylase from Aspergillus oryzae (EC 3.2.1.1) were lessened by diazo coupling of glycosides or aniline.12 Whether the decrease in activity was due to the modification of critical residues, or to the introduction of aromatic structures, is not yet clear however, enzymes subjected to the diazocoupling conditions in the absence of the diazonium salts retained their activity, implying that the reaction conditions themselves were not responsible for the loss of activity. 

An algorithm based upon a dynamic programing concept has been described by Jernigan et al. for minimizing the free energy of a polypeptide, and utilized for secondary structure prediction. In a study with the aid of UNICEPP of the binding of flexible substrate molecules within the cleft region of lysozyme (EC... 

McCammon et al. have simulated the molecular dynamics of a globular protein molecule, bovine pancreatic trypsin inhibitor, and the water strongly bound to it, to provide, since the rich variety of motions at ordinary temperatures is indicated, an improved picture in comparison to the crystal structure. Fluctuations in some rotation angles tend to correlate with others, thus conserving overall structure, but large scale concerted motions are also demonstrated. The structure of water around lysozyme (EC 3.2.1.17) has been investigated by the Metropolis method, all molecules of the crystal structure being present, ... 

Leitch EC, WiUcox MD. Lactoferrin increases the susceptibility of S. epidermidis biofUms to lysozyme and vancomycin. Curr Eye Res 1999 19(1) 12-19. 

Lysozyme (iV-acetylmuramide glycano-hydrolase, EC 3.2.1.17) from hen-egg white was the first enzyme used in homogeneous EIA (Ru-benstein et al., 1972) and is employed for a number of assays (Table 10.15). 

PPDK from Microbispora rosea subsp. Aerata (EC2.7.9.1) and thermostable Luciola cruciata firefly luciferase (EC 1.13.12.7) were obtained from Kikkoman Co. (Chiba, Japan). Pyrophosphate, Lysozyme and Proteinase K were purchased from Wako Pure Chemical Industries, Ltd (Osaka, Japan). dNTP Mixture, Taq DNA Polymerase and lOx PCR buffer were acquired from Takara Shuzo Co., Ltd (Osaka, Japan). Primers were synthesized by Takara Shuzo Co., Ltd (Osaka, Japan). Luciferin was obtained from Sigma Chemical Co (St. Louis, MO). Perfect match (PCR Enhancer) was manufactured by Toyobo. Other reagents were of analytical grade. 

Strong acids cleave C. into D- glucosamine (chitosa-mine) and acetic acid. On decomposition with alkalis, acetates and the weakly basic deacetylated, partially depolymerized, and crystallizable chitosan are formed the latter can form gels and films. The chiti-nases (EC 3.2.1.14) found in snail stomachs, some mold fungi, and bacteria can - like some lysozymes -dissolve C. The thus formed chitobiose, the disaccharide of P-1,4-linked NAG, is then cleaved to monomers by chitobiase (EC 3.2.1.30). Tlie formation of C. is catalyzed by the enzyme chitin synthase (EC 2.4.1.16). The activity of, e.g., the insecticide diflubenzurone is based on inhibition of this enzyme. 

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