The kinetics of the hydrolysis of 2-naphthyl β-D-glucuronide

Abstract

The rate of hydrolysis of 2-naphthyl-β-D-glucuronide at 90·1° follows a law of the form: rate =k₁[un-ionised glucuronide]+k₂[un-ionised glucuronide]h₀ whereas that for the hydrolysis of 2-naphthyl β-D-glucoside follows a law of the form: rate =k₂[glucoside]h₀. This difference leads to the glucoside being hydrolysed 45 times faster than the glucuronide in 1M-hydrochloric acid but 35 times slower at pH 4·79°. The term ‘k₁[un-ionised glucuronide]’ in the rate law for the hydrolysis of the glucuronide is considered to arise from a specific-hydrogen-ion-catalysed hydrolysis of the form with the carboxy-group ionised. The relevance of these results to earlier discussions of the hydrolysis of glycuronides in terms of k_obs and apparent entropies of activation is discussed.