Influence of Several Effectors on the Structure-Activity Relationship of Spleen Phosphodiesterase

The influence of Mg(II) and organic solvents on the structure-activity relationship of spleen phosphodiesterase II was analyzed using UV and fluorescence spectroscopies. An increase in the RNase activity found in the presence of Mg(II) was related to the enzyme-Mg(II) interaction detected by UV spectroscopy. In the fluorescence spectra of phosphodiesterase strong hypochromic and bathochromic effects were observed when RNA was present at a concentration (52 μg ml−1) of the same magnitude as the concentration that inhibits the activity (Ki = 40 μg ml−1). The strong quenching observed in the presence of RNA shows the importance of large dynamic and static quenching of the Trp residues of the e…