PMID: 27291073

Authors:

Abe Y, Kubota M, Takazaki S, Ito Y, Yamamoto H, Kang D, Ueda T, Imoto T

Title:

Effect on catalysis by replacement of catalytic residue from hen egg white lysozyme to Venerupis philippinarum lysozyme.

Journal:

Protein Sci. 2016 Jun 13. doi: 10.1002/pro.2966.

Abstract:

Asn46Asp/Asp52Ser or Asn46Glu/Asp52Ser hen egg white lysozyme (HEL) mutant was designed by introducing the substituted catalytic residue Asp46 or Glu46, respectively, based on Venerupis philippinarum (Vp) lysozyme structure as a representative of invertebrate-type (i-type) lyzozyme. These mutations restored the bell-shaped pH-dependency of the enzyme activity from the sigmoidal pH-dependency observed for the Asp52Ser mutant. Furthermore both lysozyme mutants possessed retaining mechanisms like Vp lysozyme and HEL. The Asn46Glu/Asp52Ser mutant, which has a shorter distance between two catalytic residues, formed a glycosyl adduct in the reaction with the N-acetylglucosamine oligomer. Furthermore, we found the accelerated turnover through its glycosyl adduct formation and decomposition. The turnover rate estimated from the glycosyl formation and decomposition rates was only 20% of the observed hydrolysis rate of the substrate. Based on these results, we discussed the catalytic mechanism of lysozymes. This article is protected by copyright. All rights reserved.