Left-sided substrate binding of lysozyme: evidence for the involvement of asparagine-46 in the initial binding of substrate to chicken lysozyme.
The "right-sided" and "left-sided" substrate binding modes at the lower saccharide binding subsites (D-F sites) of chicken lysozyme were investigated by utilizing mutant lysozymes secreted from yeast. We constructed the following mutant lysozymes; "left-sided" substitution of Asn46 to Asp, deletion of Thr47, and insertion of Gly between Thr47 and Asp48 and "right-sided" substitution of Asn37 to Gly. Analyses of their activities and substrate binding abilities showed that Asn46 and Thr47 are involved in the initial enzyme-substrate complex and Asn37 is involved in the transition state. These results support an earlier proposal that interactions between substrate and residues at the left side of lysozyme stabilize a catalytically inactive enzyme-substrate complex, while interactions between substrate and residues at the right side stabilize the catalytically active complex [Pincus, M. R., & Scheraga, H. A. (1979) Macromolecules 12, 633-644]. These results are also consistent with the proposed kinetic mechanism for lysozyme reaction that the rearrangement of an initial enzyme-substrate complex (beta-complex) to another complex (gamma-complex) is required for catalytic hydrolysis [Banerjee S. K., Holler, E., Hess, G. P., & Rupley, J. A. (1975) J. Biol. Chem. 250, 4355-4367].
Inoue
M
M
Faculty of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan.
Yamada
H
H
Yasukochi
T
T
Miki
T
T
Horiuchi
T
T
Imoto
T
T
D000595:Amino Acid Sequence; D000818:Animals; D001216:Asparagine; D001483:Base Sequence; D001665:Binding Sites; D002645:Chickens; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009113:Muramidase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D009838:Oligodeoxyribonucleotides; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
D009838:Oligodeoxyribonucleotides; D011994:Recombinant Proteins; D001216:Asparagine; D009113:Muramidase