Purification of an alkaline phosphatase-lipoprotein-X complex

An alkaline phosphatase isoenzyme was observed in an abnormal position in the agar-agarose gel pattern of sera from several patients suffering from intrahepatic and extrahepatic cholestasis. We purified this isoenzyme, by gel filtration and affinity chromatography, from the serum of a patient suffering from extrahepatic cholestasis. Analysis demonstrated an alkaline phosphatase-lipoprotein-X complex with a relative molecular mass of at least 669,000. We discuss the interpretation of alkaline phosphatase isoenzyme patterns produced by different techniques.