The mechanism of ficin-catalysed reactions

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Abstract
The kinetics of ficin-catalyzed hydrolyses of benzoyl-L-argmine ethyl ester, methyl hippurate and of the corresponding amides was studied under a variety of conditions of temperature, pH, ionic strength and dielectric constant. From the results of these experiments it can be concluded that 3 reactive groups are necessary for the catalytic action of ficin; these are -SH, NH3 + and CO2-. A reaction sequence between enzyme and substrate is proposed which involves the rapid formation of a loose enzyme-substrate compound, a subsequent acylation of the enzymic-SH group by the carbonyl of the substrate and finally the decomposition of the acyl enzyme. Reaction mechanisms for the 2d and 3d step can be formulated by analogy with homogeneous bifunctional catalysis.
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