Effect of methanol on the activity and conformation of acid phosphatase from the prawn Penaeus penicillatus

Prawn (Penaeus penicillatus) acid phosphatase (EC 3.1.3.2) catalyzes the no nspecific hydrolysis of phosphate monoesters. The effects of some pollutant s in sea water on the enzyme activity results in the loss of the biological function of the enzyme, which leads to disruption of phosphate metabolism in cells. This paper analyzes the effects of methanol on the activity and c onformation of prawn acid phosphatase. The results show that low concentrat ions of methanol can lead to reversible inactivation. Inhibition of the enz yme by methanol is classified as non-competitive inhibition, and the inhibi tion constant (K-i) is 8.5%. Conformational changes of the enzyme molecule in methanol solutions of different concentrations were measured using fluor escence emission, differential W-absorption, and circular dichroism spectra . Increased methanol concentrations caused the fluorescence emission intens ity of the enzyme to increase. The ultraviolet difference spectra of the en zyme denatured with methanol had two negative peaks, at 222 and 270 nm, and a positive peak at 236 nm, The changes in the fluorescence and ultraviolet difference spectra reflected the changes of the microenvironments of trypt ophan and tyrosine residues of the enzyme. The CD spectrum changes of the e nzyme show that the secondary structure of the enzyme also changed some. Th ese results suggest that methanol is a non-competitive inhibitor and the co nformational integrity of the enzyme is essential for its activity.