Nitrophenyl trimethylacetate

Bender and Marshall [J. Am. Chem. Soc., 90 (201), 1968] have studied the enzymatic hydrolysis of p-nitrophenyl trimethylacetate by elastase to produce p-nitrophenol. These authors have proposed the following mechanism for this reaction. 

S = substrate = p-nitrophenyl trimethylacetate P = product = p-nitrophenol A = trimethylacetic acid kx = 150 m3/mole-ksec k2 = 2.60 ksec-1... 

CHj)3C.CO.OE, by attack of the serine hydroxyl group on the carbonyl carbon atom of 4-nitrophenyl trimethylacetate. This attack is assisted by proton removal from the hydroxyl group by the charge-relay mechanism, Scheme 13. It is also considered that breakdown of trimethylacetylchymo-trypsin may be assisted by the charge-relay mechanism. In this case, a proton... 

Fig. 21 Rate-pH dependence of the acylation and deacylation steps in the chymotrypsin-catalysed hydrolysis of 4-nitrophenyl trimethylacetate...

By means of Eqn. 17 and stopped-flow studies at various values of Sq, k2, and kj, can be separately determined and studied. For carboxypeptidase Y, which also shows such burst kinetics with 4-nitrophenyl trimethylacetate (I), enzyme preparations with differing amounts of attached carbohydrate, reacted with closely similar steady-state parameters K, k ) but differences were apparent for presteady-state parameters (k2> [14]. 

Intramolecular acyl migration 2-Hydroxymethyl-4-nitrophenyl trimethylacetate 6... 

An example of conformational catalysis is shown in the intramolecular acyl transfer of 2-hydroxymethyl-4-nitrophenyl trimethylacetate (6) (Scheme 4). The... 

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