Hydrolysis with phosphate esterases

Gana et al. developed and validated a reversed-phase high performance liquid chromatographic method for the kinetic investigation of the chemical and enzymatic hydrolysis of benazepril hydrochloride [37]. Kinetic studies on the acidic hydrolysis of benazepril hydrochloride were carried out in 0.1 M hydrochloric acid solution at 50, 53, 58 and 63°C. Benazepril hydrochloride appeared stable in pH 7.4 phosphate buffer at 37°C, and showed susceptibility to in vitro enzymatic hydrolysis with porcine liver esterase (PLE) in a pH 7.4 buffered solution at 37°C. 

As early as 1973, Zemer and Dudman reported the kinetic resolution of a P-stereogenic phosphate triester (butylmethyl(p-nitrophenyl)phosphate) by hydrolysis with beef and horse serums, albeit with very low efficiency. The first efficient resolutions of phosphorus stereocentres with enzymes were independently reported in 1994 by two groups. Serreqi and Kazlauskas studied the enantioselective hydrolysis of pendant acetate groups in chiral racemic phosphines and phosphine oxides mediated by several commercially available lipases and esterases, under kinetic resolution conditions i.e. the reaction was stopped at 50% conversion). In general, enantioselectivities were low to moderate, but for one substrate promising results were obtained (Scheme 6.54). 

As outlined in Figure 3, the hydrolysis of paraoxon by human serum A-esterase(s) is very similar to the phosphorylation of B-esterases, such as acetylcholinesterase, by paraoxon. Both reactions involve an initial binding of paraoxon to the enzyme, followed by a rapid conformational change that produces diethyl phosphate and p-nitrophenol from paraoxon. p-Nitrophenol is quickly released from the enzyme, leaving diethyl phosphate covalently bound to enzyme. At this point, A-esterase quickly releases diethyl phosphate as a result of interacting with a water molecule. However, B-esterases, such as acetylcholinesterase, retain the diethyl phosphate for a much longer period of time, thereby resulting in inhibition of the enzyme. 

The chemistry of complex lipids is dominated by regioselective hydrolysis reactions of (1) the glyceryl fatty acid esters and (2) phosphate diesters. Both types of reactions are routinely performed with the corresponding esterases. A large variety of lipid active transferase enzymes is also commercially available. Phospholipases Aj, A, C, and D, for example, split any of the four ester bonds of a phospholipid regioselectively. The product without a fatty acid side chain at C2 of glycerol is called a lysophospholipid. Lecithin-cholesterol-acyltransferase transfers the fatty acid at C2, often linoleic acid, to the OH group at C3 of cho-... 

Many pesticides have ester bonds, amide bonds, or substituted phosphate ester groups that are susceptible to hydrolysis by esterases. Enzymes with carboxylesterase (CarbE) and amidase activities are found in both microsomal and soluble fractions from a variety of tissues. Although functionally ester and amide groups are different, no CarbE has been found that does not have hydrolytic activity toward the corresponding amide and vice versa. 

The biocatalytic acetylation of prochiral bis(hydroxymethyl)phenylphosphine oxide 277 and the biocatalytic hydrolysis of prochiral bisfmethoxycarbonylmethyl) phenylphosphine oxide 279 was subjected to hydrolysis in a phosphate buffer in the presence of several hydrolases (PLE, PPL, AHS, Amano-AK, and Amano-PS), of which only porcine liver esterase (PLE) proved to be efficient. The best results were attained with Pseudomonas fluorescens lipase (PFL) in chloroform which allowed the compound 278 to be obtained in yields up to 76% and with ee up to 79%. Absolute configuration of the (5)-278 was determined by means of chemical correlation to the earlier described compound (/ )-282, as shown in Scheme 91 [185]. 

Bovine erythrocyte CA shows both oxonase and esterase activity with dimethyl 2,4-dinitrophenyl phosphate and 2,4-dinitrophenyl acetate respectively. Both processes show similar pH dependencies with pJTa values of 7.37 (oxonase) and 7.53 (esterase) and maximum activity in the basic form. Inhibition by acetazol-amide at pH 8.95 yields the same inhibition constant for both reactions, implying involvement of the active-site zinc to the same extent in both processes. Methyl and ethyl pyruvate are susceptible to hydrolysis,... 

---