Kinetic principles and enantioselectivity of the action of penicillin acylase in the hydrolysis of n-phenylacetyl derivatives of 1-aminoethylphosphonic acid and its estersстатья
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Дата последнего поиска статьи во внешних источниках: 27 мая 2015 г.
Местоположение издательства:Road Town, United Kingdom
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Аннотация:The ability of penicillin acylase (EC 3.5.1.11) from E. coli ATCC9637 to catalyze the hydrolysis of N-phenylacetyl derivatives of 1-aminoethylphosphonic acid, as well as its esters, has been detected for the first time. On the basis of a study of the kinetics of the enzymatic hydrolysis of such compounds, a general reaction scheme is proposed, taking into account the hydrolysis of L- and D-enantiomers of the substrate, competitive inhibition by the reaction product-phenylacetic acid (inhibition constant 35-mu-M), as well as inhibition by the substrate with the formation of a ternary inactive complex E(S(L))2 with inhibition constant 0.07 M. For the N-phenylacetyl derivative of 1-aminoethylphosphonic acid the following kinetic parameters were determined: catalytic constant (k) and Michaelis constant (K(m)) of enzymatic hydrolysis for the L- and D-forms of the substrate, equal to 237 sec-1 and 3.7 10(-3) M, 0.3 sec-1, and 2.7 . 10(-3) M, respectively. In the case of N-phenylacetyl derivatives of the dimethyl and diisopropyl esters of 1-aminoethylphosphonic acid, for the L-enantiomers of the substrates k and K(m) were determined, equal to 148 sec-1 and 6.8 . 10(-4) M, 134 sec-1 and 6.2 . 10(-4) M, respectively. For the D-enantiomers of these substrates, the second-order constants (k/K(m)) were determined, equal to 96 and 120 M, respectively. The stereospecificity of the action of penicillin acylase in the hydrolysis of the N-phenylacetyl derivative of 1-aminoethylphosphonic acid, expressed as the ratio of the bimolecular rate constants of the hydrolysis of the L- and D-forms, is 5.8 . 10(4); for the corresponding derivatives of the esters this value is somewhat lower: for the diisopropyl ester 1.8 . 10(3), and for the dimethyl ester 2.3 . 10(3).