Membrane Cholesterol Content and Malignancy of Ehrlich Ascites-Carcinoma Cells

If these three high-pH complications are corrected for, then the variation of kcat with pH in all three cases is governed by a single, non-essential ionization, around pH8.2 in the presence of Mg2+, and pH6 in its absence. It is tempting to equate this ionization with that obtained for conventional substrates [pH8.4 with Mg2+ and pH6.5 without (Tenu et al., 1971)], but, if the same species is responsible, proton loss eliminates activity against conventional substrates and improves activity against these salts. That the only accessible ionization should be non-essential confirms our picture of the catalytic mechanism of their hydrolysis, a process accomplished preponderantly by induction of strain on binding, and influenced by ionization of active-site groups only through the change in ionic environment.