Activity and conformation of bovine pancreatic ribonuclease A in reverse micelles formed by dodecylammonium butyrate and water in cyclohexane

The enzymatic activity of bovine pancreatic ribonuclease A (RNase A, E.C.3.1.27.5.) solubilized in reverse micelles formed by dodecylammonium butyrate and in cyclohexane-water has been investigated with the use of cytidine 2',3'-cyclic phosphate (CP) as the substrate. The pH profile of the enzyme activity in the hydrocarbon micellar solution is similar to that in water, and the initial velocity of CP hydrolysis decreases with the increase in water content. The enzyme obeys Michaelis-Menten kinetics in the investigated concentration range and there is an enhanced turnover number accompanied by an increased K-m value in reverse micelles. The conformation of RNase A in reverse micelles was investigated by UV and FT-IR spectroscopy. Both UV and FT-IR data suggest that the structure of the enzyme in reverse micelles with high water content is similar to that in water, but larger structure differences were found at the lower water content.