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Updated: Aug 23, 2026

The Importance of Correct Protein Concentration for Kinetics and Affinity Determination in Structure-function Analysis
Published on: March 17, 2010
His507 of acylaminoacyl peptidase stabilizes the active site conformation, not the catalytic intermediate
András L Kiss1, Zoltán Szeltner, Vilmos Fülöp
1Institute of Enzymology, Biological Research Center, Hungarian Academy of Sciences, P.O. Box 7, H-1518 Budapest 112, Hungary.
Abstract:
Acylaminoacyl peptidase is a member of the prolyl oligopeptidase family. Amino acid sequence alignment suggests that the stabilization of the tetrahedral intermediate should be mediated by His507 rather than by a tyrosine residue found in the other family members of this serine peptidase group. The pH dependence of k(cat)/K(m) did not reveal any effect of His507. Substitution of an alanine for His507 gave the same bell-shaped pH rate profile with the same pK(a) values (7.0 and 8.7). However, the value of the rate constant was 85 times lower with the modified enzyme, which indicated that His507 is an important residue that is probably involved in the formation of the 3-dimensional structure.
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