Initiation of Altered Heparan Sulphate on β-D-Xyloside in Rat Hepatocytes

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Abstract
Inhibition of protein synthesis by cycloheximide (10-3 M) reduced the incorporation of [35S]sulfate into heparan sulfate to about 5% of untreated hepatocytes. Addition of p-nitrophenyl .beta.-D-xyloside could partially revert this inhibitory effect. The sulfated material isolated from the cell layer or secretions of hepatocytes grown in presence of cycloheximide and p-nitrophenyl .beta.-D-xyloside were mostly free heparan sulfate chains not bound to core protein. Covalent association of .beta.-xyloside to the heparan sulfates was demonstrated for heparan sulfate synthesized in the presence of [35S]sulfate, cycloheximide and the fluorogenic 4-methylumbelliferyl .beta.-D-xyloside. .beta.-Xylosides served as an initiator of heparan sulfate chain synthesis in rat hepatocytes only in the absence of protein synthesis. Heparan sulfates primed on artificial .beta.-xylosides are slightly smaller in molecular size and are more sulfated than chains linked to core protein.