Membrane-associated sialidase of rat liver and its decrease in hepatomas.
Using the particulate fraction of tissue homogenate, plasma membrane-associated sialidase was assayed at pH 4.5 with bovine brain mixed gangliosides as the substrate. The activity was lower in rat hepatoma induced by 3'-methyl-4-dimethylaminoazobenzene (MeDAB) and transplantable AH-109A rat hepatoma than in normal rat liver. The enzyme was almost quantitatively solubilized from liver particulate fraction by using 0.5% (w/v) sodium deoxycholate plus 0.2% (w/v) Triton X-100. When chromatographed on DEAE-cellulose, the solubilized activity emerged as a single peak. The enzyme thus obtained was maximally active at pH 4.5, and readily hydrolyzed mixed gangliosides but was less active toward 4-methylumbelliferyl-alpha-N-acetylneuraminic acid, 3'-sialyllactose and fetuin. The corresponding enzyme from MeDAB-induced hepatoma was indistinguishable from the liver enzyme in terms of ease of solubilization, pH-activity relationship, chromatographic behavior and substrate preference. It therefore appears that the plasma membrane-associated sialidase of hepatomas differs from that of liver only in the tissue level of activity.
D000818:Animals; D002462:Cell Membrane / Q000201:enzymology; D005732:Gangliosides / Q000378:metabolism; D008099:Liver / Q000201:enzymology*; D008114:Liver Neoplasms, Experimental / Q000201:enzymology*; D008297:Male; D009439:Neuraminidase / Q000032:analysis* / Q000302:isolation & purification; D051381:Rats; D011919:Rats, Inbred Strains
D005732:Gangliosides; D009439:Neuraminidase