INFLUENCE OF STATE OF MOLECULAR AGGREGATION ON ENZYMIC HYDROLYSIS OF ARYLSULFATE ESTERS

While the acid‐catalyzed hydrolysis of potassium dichloronaphthyl sulfate is considerably enhanced when the substrate is bound to the surface of a micelle‐forming surfactant, the enzyme catalyzed hydrolysis of this substrate exhibits a marked overall inhibition when the substrate is bound to the same surfactant. A plot of the rate of enzymic hydrolysis of that fraction of the substrate bound to the surfactant micelle versus surfactant concentration exhibits a sharp maximum. It is postulated that this maximum can be attributed to a gross change in the composition or structure of the surfactant‐substrate micelle, such that the required “fit” of the bound substrate on the enzyme surface is sterically blocked. This “critical” surfactant concentration is also evidenced by an abrupt change in the extent of substrate‐surfactant interaction under similar conditions. The rate of hydronium ion‐catalyzed hydrolysis of potassium dichloronaphthyl sulfate bound to the same surfactant exhibits no such maximum. Copyright © 1969 Wiley‐Liss, Inc., A Wiley Company