Open AccessStructure‐Activity Relationship in the Urokinase Hydrolysis of α‐ N ‐Acetyl‐ l ‐lysine Anilides
Author(s) -
PETKOV Dimiter,
CHRISTOVA Evdokia,
POJARLIEFF Ivan,
STAMBOLIEVA Nikolina
Publication year - 1975
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1975.tb03902.x
Subject(s) - chemistry , reaction rate constant , substrate (aquarium) , substituent , hydrolysis , aniline , lysine , tetrahedral carbonyl addition compound , stereochemistry , urokinase , enzyme , reaction rate , rate determining step , kinetics , limiting , medicinal chemistry , catalysis , organic chemistry , amino acid , nucleophile , biochemistry , physics , geology , medicine , oceanography , quantum mechanics , mechanical engineering , engineering
The absence of both nonproductive binding and substrate activation and also the good solubility of the substrates make the urokinase‐catalysed hydrolysis of specific anilides a very suitable reaction for substrate structure–enzyme activity studies. Derivatives of α‐ N ‐acetyl‐ l ‐lysine anilide with high σ ‐value substituents in the aniline ring were synthesized. Rate constants k cat. and apparent Michaelis‐Menten constants K m(app.) are presented. From the substituent dependence of k cat. and from the fact that k cat. is 13 to 37 times smaller than the deacylation rate constant it is concluded that the rate‐limiting step proceeds prior to deacylation. The catalytic rate constant k cat. obeys a linear free‐energy relationship of the Hammett type with ϱ=+ 0.72. Two different mechanisms implied by the results obtained from the model reaction (specific base and general acid‐base catalysed hydrolysis of N ‐acetylglycine anilides under extreme conditions) are proposed in order to account for this positive and low ϱ‐value. In the first mechanism the breakdown of an enzyme tetrahedral intermediate is rate‐limiting, while in the second one its formation controls the overall rate. The discrimination between the two mechanisms, however, could not be found.