Identification of classical, novel, and atypical protein kinase C isoenzymes in the bovine parathyroid.

Because phospholipid metabolism leading to the activation of protein kinase C (PKC) may play a key regulatory role in the degradation and secretion of PTH, we examined parathyroid cell fractions for the presence of various PKC isoenzymes. Hydroxylapatite chromatography identified the classical PKCs, alpha and beta, but not gamma in parathyroid cell extracts. Western blot analysis confirmed the presence of PKC alpha and beta in these extracts. Of the so-called novel PKCs, Western blot analysis revealed the presence of only one isoenzyme, novel PKC epsilon in parathyroid cell soluble extracts. Western blot analysis using an antibody to the C-terminus of the atypical isoenzyme, PKC zeta, identified a protein of lower molecular weight in addition to PKC zeta. This lower molecular weight protein presumably represents PKC lambda, which shares a high degree of C-terminal sequence similarity with PKC zeta. These findings suggest the possibility that members of all three groups of the PKC family are present and may play a regulatory role in the bovine parathyroid cell.