Characterization of calcium and phospholipid dependent protein kinase in isolated rat adipocytes

Calcium and phospholipid-dependent protein kinase (protein kinase C) from isolated rat adipocytes has been partially purified using DEAE-Sepharose CL-6B and characterized. The enzyme was shown to have similar properties as the kinase isolated from brain or spleen. When histone was used as substrate, an equal amount of cAMP-dependent and calcium and phospholipid-dependent kinase activity was detected from the DEAE Sepharose CL-6B fractions. The major part of protein kinase C (72%) was isolated from the soluble adipocyte fraction. Of the membranous fractions, the plasma membrane exhibited the highest specific activity. The protein kinase preparations bound [3H]-phorbol-12,13-dibutyrate (PDBU) with high affinity (Kd = 2 nM) and the number of PDBU binding sites per cell was calculated to 63 000.