Lysozyme acetylated derivative

Materials. Proteins. The preparation of l-14C-acetyl derivatives of bovine /3-casein A and hen egg white lysozyme has been described (12, 13). Modification of /3-casein involved reaction of the protein with l-14C-acetic anhydride so that two lysine residues along the disordered, single polypeptide chain of 209 amino acids (11) were acetylated. A similar procedure was done with lysozyme so that one or two lysine residues on the exterior of the globular protein (14) were acetylated. These modifications ensured that the derivatives which were isolated in the lyophilized state had suitable specific activities (typically 1.5 juC/mg dry protein). The modification slightly increased the surface activity of lysozyme but not that of /3-casein (12, 13) in this paper the l-14C-acetyl derivatives are referred to as /3-casein and lysozyme. 

The accessibility of chitin, mono-O-acetylchitin, and di-O-acetylchitin to lysozyme, as determined by the weight loss as a function of time, has been found to increase in the order chitin < mono-O-acetylchitin < di-O-acetylchitin [120]. The molecular motion and dielectric relaxation behavior of chitin and 0-acetyl-, 0-butyryl-, 0-hexanoyl and 0-decanoylchitin have been studied [121,122]. Chitin and 0-acetylchitin showed only one peak in the plot of the temperature dependence of the loss permittivity, whereas those derivatives having longer 0-acyl groups showed two peaks. 

Before the introduction of site-directed mutagenesis, chemical modification was the predominant means of altering a specific amino acid the earliest report with lysozyme was from Parsons and Raftery (241), who prepared the ethyl ester derivative of Asp-52 by reaction with triethyloxonium fluoroborate the modified enzyme lost catalytic function but not substrate affinity. An ethyleneimine reaction product of Asp-52 has also been prepared with similar effects on catalysis (242). Sharon and co-workers modified and then regenerated Asp-52 to eliminate concern that inactivation results from experimental manipulation rather than specific amino acid modification (243, 244). Thus, Asp-52 was first esteri-fied with an epoxypropyl-jS-glycoside derivative of di-(/V-acetyl-D-glucosamine), then reduced to homoserine or hydrolyzed to return the free aspartate. Both the... 

C -(2-Acetamido-2-deoxy 3-D-glucosyl)-(l 4)-iV-acetyl muramoyl-L-alanyl-D-isoglutamine (31), the dipeptide derivative of the disaccharide isolated from lysozyme digests of bacterial cell walls, has been prepared in a fourteen-step sequence from 2-acetamido-2-deoxy-D-glucose. The dipeptide disaccharide derivative (32) isolated from lysostaphin endo-l3-D-2-acetamido-2-deoxy-glucan-ase digests of cell walls has also been synthesized (Scheme 5). ... 

Chitosan is a linear polysaccharide of (l-4)-glycosidic bonds derived from the exoskeletons of animals such as crustaceans, mollusks, and insects (Alves and Mano, 2008, Lu et al., 2009). It can also be extracted from the fungal fermentation processes. It is a biocompatible and biodegradable cationic biopolymer obtained from deacetylation of chitin in an alkaline environment (Alves and Mano, 2008), but is known to cause slight inflammation in mammals. The biodegradation rate of chitosan is determined by the residual acetyl content, a parameter that can be easily tuned. The major pathway for the biodegradation in vivo is through lysozyme which depolymerizes the polysaccharide. It has been used for many medical applications due to its low-toxicity and acceptable biocompatibility. Recently, temperature-sensitive variations of chitosan have been developed. 

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