Effects of Spin‐Labeled Stearates on Duck Erythrocyte Adenylate Cyclase

The effects of various spin-labeled stearates on duck erythrocyte adenylate cyclase were investigated. Only 2-(3-carboxypropyl)-4,4-dimethyl-2-tridecyl-3-oxazolidinyloxyl caused an increase in adenylate cyclase activity. It increased the basal rate by about 50%, and the activities stimulated by isoproterenol and isoproterenol plus guanosine 5′-[β,γ-imido]triphosphate by 35%. Upon analysis of the width parameter Δ1 in the electron spin resonance spectra for both the basal enzyme activity and the stimulation obtained with effectors such as guanosine 5′-[β,γ-imido]triphosphate, isoproterenol, isoproterenol plus guanosine 5′-[β,γ-imido]triphosphate and NaF, a correlation of the changes of modification in adenylate cyclase activities was found. These findings suggest that the molecular environment of the enzyme has been modified.