Subcellular distribution of 2?,3?-cyclic nucleotide-3?-phosphodiesterase in cat peripheral nerve

Subcellular distribution of 2?,3?-cyclic nucleotide-3?-phosphodiesterase (CNPase) in desheathed, saline perfused cat sciatic nerve is reported. CNPase specific activity was enriched in the total particulate (P(2)) fraction and was low in the soluble (S(2)) fraction. "Light-myelin" floating above the 0.60 M sucrose phase had the highest CNPase activity, 2.5-fold over the crude homogenate (CH). By contrast, enzyme activity in "heavy myelin" floating above the 0.85 M sucrose interface was equal to that of the CH and accounted for only 12% of total activity. CNPase activity in the membranes floating above the 0.25 and 0.60 and 0.85 M sucrose phases comprised nearly 70% of the total CNPase activity. The "light myelin" fraction floating above the 0.60 M sucrose accounted for approx. 51% of the total CNPase activity. SDS-PAGE of membranes individually harvested from above the 0.25 and 0.60 and 0.85 M sucrose phases revealed the presence of myelin-specific proteins (P(0), P(1); and P(2)). Electron microscope examination demonstrated the presence of myelin in each membrane fraction. The results of this study show that the majority of CNPase activity is associated with "light myelin" in cat peripheral nerve.