Kinetics of enzymatic hydrolysis of aromatic mono carboxylic acid and di carboxylic acid quaternary aminoalkyl esters by butyryl cholin esterase from horse blood serum
Volkova, R.I.; Dmitrieva, E.N.
Biokhimiya 41(2): 264-275
1976
Accession: 005783284
The kinetics of hydrolysis of benzoylcholine (BzCh), phehylpropionic acid choline ester (PK-157), suberic acid dicholine ester (D-6) p-phenylenediacetic (PK-139), p-phenylenedipropionic (PK-154 and PK-155), p-phenylenediacryc (PK-150 and PK-151) and phtalic (PK-105) acids diaminoalkyl esters by horse blood serum butyrylcholinesterase (BuChE) was studied. Hydrolysis constants Km, V and Kss were estimated by various graphic methods. PK-157 ester had a high affinity for BuChE, its V being 20 times as high and Km 20 times those for acetylcholine (ACh). The highest V value was found for D-6 in the diesters. Hydrolysis of aromatic dicarboxylic acid diesters was characterized by lower V values (0.6-10% of V for ACh) and extremely low Km values (.apprx. 10-5-10-6 M). Substrate inhibition was observed in the hydrolysis of BzCh, PK-157, D-6 and all aromatic dicarboxylic acid esters by BuChE. Formal kinetic analysis revealed that inactive complex, was formed which, corresponded to ES2 composition. The substrate inhibition for BuChE and its increase may be due to the increase in the size and in the rigidity of the acyl part of the molecule in the substrates studied.