Properties of phospholipase C in isolated olfactory cilia from the channel catfish (Ictalurus punctatus).

1. Cilia were isolated from the olfactory epithelium of the channel catfish (Ictalurus punctatus) with improved yield. The isolated preparations were enriched in cilia as indicated by electron microscopy, tubulin immunoblotting and identification of a ciliary-specific glycoprotein. 2. The isolated cilia preparations exhibited phospholipase C (EC 3.1.4.11) activity. The enzyme was maximally active at pH 6.7. 3. Analysis of inositol phosphates resulting from the hydrolysis of exogenous radiolabeled phosphatidylinositol-4,5-bisphosphate in isolated cilia, indicated that inositol triphosphate was the major (90%) inositol phosphate produced. 4. Three molecular forms of the enzyme, Mr greater than or equal to 100,000, 82,000 and 60,000 were resolved by gel filtration chromatography from a cytosolic fraction from the olfactory epithelium.