Heparan sulphate-degrading endoglycosidase in liver plasma membranes.
An endoglycosidase is described in isolated liver plasma membranes that brings about a rapid and selective degradation of membrane-associated heparan sulphate, pre-labelled biosynthetically with Na2(35)SO4. The enzyme attacked mainly the polysaccharide chains of a hydrophobic membrane proteoglycan and it had little effect on a proteoglycan that could be displaced from the membranes with 1.0 M-NaCl. The highest activity was measured in the pH range 7.5-8.0, and the enzyme was almost completely inhibited below pH 5.5. Breakdown of susceptible polysaccharide chains was fast, being complete in 20-30 min. The major oligosaccharide fraction (Mr approx. 6000) produced by the enzyme was considerably smaller than the intact heparan sulphate chains. Enzyme activity was retained in membranes solubilized in 1% (v/v) Triton X-100. The high pH optimum and plasma-membrane association distinguish this enzyme from other heparan sulphate-degrading endoglycosidases that have acid pH optima and may be of lysosomal origin. A plasma-membrane endoglycosidase could modulate cellular interactions mediated by heparan sulphate, and/or release biologically active fragments of the polysaccharide from the cell periphery.
Gallagher
J T
JT
Cancer Research Campaign Department of Medical Oncology, Christie Hospital, University of Manchester, U.K.
Walker
A
A
Lyon
M
M
Evans
W H
WH
D000818:Animals; D002462:Cell Membrane / Q000201:enzymology; D011508:Chondroitin Sulfate Proteoglycans / Q000378:metabolism; D002846:Chromatography, Affinity; D002850:Chromatography, Gel; D005966:Glucuronidase; D006026:Glycoside Hydrolases / Q000378:metabolism*; D019812:Heparan Sulfate Proteoglycans; D006497:Heparan Sulfate / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008099:Liver / Q000201:enzymology; D011134:Polysaccharides / Q000378:metabolism; D011509:Proteoglycans / Q000378:metabolism; D051381:Rats; D000099175:Heparanase
D011508:Chondroitin Sulfate Proteoglycans; D005966:Glucuronidase; D006026:Glycoside Hydrolases; D019812:Heparan Sulfate Proteoglycans; D006497:Heparan Sulfate; D011134:Polysaccharides; D011509:Proteoglycans; D000099175:Heparanase