Amino acid residues in subsites e and f responsible for the characteristic enzymatic activity of duck egg-white lysozyme. 2002

Shunsuke Kawamura, and Gen Toshima, and Taiji Imoto, and Tomohiro Araki, and Takao Torikata
Department of Bioscience, School of Agriculture, Kyushu Tokai University, Aso, Kumamoto 869-1404, Japan. skawa@ktmail.ktokai-u.ac.jp

We analyzed the enzymatic properties of duck egg-white lysozyme II (DEL), which differs from hen egg-white lysozyme (HEL) in nineteen amino acid substitutions. A substrate binding study showed that DEL binds to the substrate analog at subsites A-C in the same manner as HEL. However, the experimental time-courses of DEL against the substrate N-acetylglucosamine pentamer, (GlcNAc)(5), revealed remarkably enhanced production of (GlcNAc)(2) and reduced production of (GlcNAc)(1) as compared to in the case of HEL. Computer simulation of the DEL-catalyzed reaction suggested that the amino acid substitutions at subsites E and F (Phe34 to Tyr and Asn37 to Ser) caused the great alteration in the time-courses of DEL. Subsequently, the enzymatic reactions of mutants, in which Phe34 and Asn37 in HEL were converted to Tyr and Ser, respectively, were characterized. The time-courses of the F34Y mutant exhibited profiles similar to those of HEL. In contrast, the characteristics of the N37S mutant were different from those of HEL and rather similar to those of DEL; the order of the amounts of (GlcNAc)(1) and (GlcNAc)(2) was reversed in comparison with in the case of HEL. Enhanced production of (GlcNAc)(2) was also observed for the mutant protein, F34Y/N37S, with two substitutions. These results indicated that the substitution of Asn37 with Ser can account, at least in part, for the characteristic time-courses of DEL. Moreover, replacement of Asn37 with Ser reduced the rate constant of transglycosylation. The substitution of the Asn37 residue may affect the transglycosylation activity of HEL.

UI MeSH Term Description Entries
D007700 Kinetics The rate dynamics in chemical or physical systems.
D008969 Molecular Sequence Data Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories. Sequence Data, Molecular,Molecular Sequencing Data,Data, Molecular Sequence,Data, Molecular Sequencing,Sequencing Data, Molecular
D009113 Muramidase A basic enzyme that is present in saliva, tears, egg white, and many animal fluids. It functions as an antibacterial agent. The enzyme catalyzes the hydrolysis of 1,4-beta-linkages between N-acetylmuramic acid and N-acetyl-D-glucosamine residues in peptidoglycan and between N-acetyl-D-glucosamine residues in chitodextrin. EC 3.2.1.17. Lysozyme,Leftose,N-Acetylmuramide Glycanhydrolase,Glycanhydrolase, N-Acetylmuramide,N Acetylmuramide Glycanhydrolase
D011485 Protein Binding The process in which substances, either endogenous or exogenous, bind to proteins, peptides, enzymes, protein precursors, or allied compounds. Specific protein-binding measures are often used as assays in diagnostic assessments. Plasma Protein Binding Capacity,Binding, Protein
D002942 Circular Dichroism A change from planar to elliptic polarization when an initially plane-polarized light wave traverses an optically active medium. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed) Circular Dichroism, Vibrational,Dichroism, Circular,Vibrational Circular Dichroism
D004372 Ducks A water bird in the order Anseriformes (subfamily Anatinae (true ducks)) with a broad blunt bill, short legs, webbed feet, and a waddling gait. Duck
D004527 Egg Proteins Proteins which are found in eggs (OVA) from any species. Egg Protein,Egg Shell Protein,Egg Shell Proteins,Egg White Protein,Egg White Proteins,Egg Yolk Protein,Egg Yolk Proteins,Ovum Protein,Ovum Proteins,Yolk Protein,Yolk Proteins,Protein, Egg,Protein, Egg Shell,Protein, Egg White,Protein, Egg Yolk,Protein, Ovum,Protein, Yolk,Proteins, Egg,Proteins, Egg Shell,Proteins, Egg White,Proteins, Egg Yolk,Proteins, Ovum,Proteins, Yolk,Shell Protein, Egg,Shell Proteins, Egg,White Protein, Egg,White Proteins, Egg,Yolk Protein, Egg,Yolk Proteins, Egg
D006031 Glycosylation The synthetic chemistry reaction or enzymatic reaction of adding carbohydrate or glycosyl groups. GLYCOSYLTRANSFERASES carry out the enzymatic glycosylation reactions. The spontaneous, non-enzymatic attachment of reducing sugars to free amino groups in proteins, lipids, or nucleic acids is called GLYCATION (see MAILLARD REACTION). Protein Glycosylation,Glycosylation, Protein
D000117 Acetylglucosamine The N-acetyl derivative of glucosamine. Acetyl Glucosamine,N-Acetyl Glucosamine,N-Acetyl-beta-D-Glucosamine,N-Acetylglucosamine,beta-N-Acetylglucosamine,2-Acetamido-2-Deoxy-D-Glucose,2-Acetamido-2-Deoxyglucose,N-Acetyl-D-Glucosamine,2 Acetamido 2 Deoxy D Glucose,2 Acetamido 2 Deoxyglucose,Glucosamine, Acetyl,Glucosamine, N-Acetyl,N Acetyl D Glucosamine,N Acetyl Glucosamine,N Acetyl beta D Glucosamine,N Acetylglucosamine,beta N Acetylglucosamine
D000595 Amino Acid Sequence The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION. Protein Structure, Primary,Amino Acid Sequences,Sequence, Amino Acid,Sequences, Amino Acid,Primary Protein Structure,Primary Protein Structures,Protein Structures, Primary,Structure, Primary Protein,Structures, Primary Protein

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