Partial purification and characterization of the calcium-dependent and phospholipid-dependent protein kinase C from chick oviduct

Open Access
Publisher Website
Google Scholar
Abstract
The calcium‐dependent and phospholipid‐dependent protein kinase C is partially purified (2000‐fold) from chick oviduct cytosol by chromatography on DEAE‐cellulose, Sephadex G150 and (after affinity binding of the enzyme to phosphatidylserine‐diolein liposomes) on Bio‐Gel A‐0.5m. The enzyme is activated by phosphatidyl‐serine and calcium ions. Diolein increases the affinity of the enzyme for both cofactors and can be replaced by the tumour‐promoting phorbol ester 12‐O‐tetradecanoyl‐phorbol 13‐acetate. Phosphatidylserine can be replaced by unsaturated long‐chain fatty acids. Quercetin and phloretin inhibit the kinase reversibly competing with ATP. Several oviduct proteins are found to be phosphorylated by the partially purified enzyme. One of the substrates, a 78‐kDa protein, appears to be ovotransferrin.