UNFOLDING AND INACTIVATION OF PENAEUS PENICILLATUS ACID-PHOSPHATASE DURING DENATURATION BY GUANIDINE-HYDROCHLORIDE

The conformational changes of penaeus penicillatus acid phosphatase du ring denaturation in guanidine hydrochloride solutions were studied by following changes in the intrinsic fluorescence, ultraviolet differen ce absorption, and circular dichroism spectra. Inactivation of the enz yme in guanidine hydrochloride solutions were compared with unfolding of the enzyme molecule. The results show that the extent of unfolding in guanidine solutions measured by several different methods closely c oincide with each other and that slightly lower concentrations of guan idine are required to bring about inactivation than are required to pr oduce significant conformational changes of the enzyme molecule. At th e same concentrations, the inactivation rate constants are markedly fa ster than the rate constants for unfolding of the enzyme. The above re sults suggest that the active sites of this enzyme display more confor mational flexxibility than the enzyme molecule as a whole.