Association of the two glycosyl transferase activities of glycoprotein synthesis with low equilibrium density smooth microsomes.

Abstract

ABSTRACT Smooth microsomes of rat liver were subfractionated on a continuous sucrose gradient to isopyenic equilibrium density. All the microsomal electron-transport enzymes and phosphatases exhibit a broad distribution in the various microsomal subtractions. On the other hand, the N-acetylglucosaminyl and galactosyl transferase activities, which are known to participate in the synthesis of the oligosaccharide chain of the plasma glycoproteins, exhibit a markedly different distribution pattern. They are concentrated to a small fraction having an isopyenic equilibrium density of 1·10. These membranes represent a separate entity of the smooth microsomal fraction, the exact cellular origin of which remains to be clarified.