His507 of acylaminoacyl peptidase stabilizes the active site conformation, not the catalytic intermediate.
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.
Kiss
András L
AL
Institute of Enzymology, Biological Research Center, Hungarian Academy of Sciences, P.O. Box 7, H-1518 Budapest 112, Hungary.
Szeltner
Zoltán
Z
Fülöp
Vilmos
V
Polgár
László
L
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002384:Catalysis; D004795:Enzyme Stability; D006639:Histidine; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008969:Molecular Sequence Data; D010447:Peptide Hydrolases / Q000737:chemistry* / Q000378:metabolism*; D011487:Protein Conformation; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013552:Swine
D006639:Histidine; D010447:Peptide Hydrolases; C038220:acylaminoacyl-peptidase