Isolation and characterization of a sialidase from the starfish Asterias rubens.
The starfish Asterias rubens contains a soluble sialidase (1.4 mU/mg homogenate protein), which was purified over 500-fold to apparent homogeneity by ammonium sulfate precipitation, gel filtration and affinity chromatography on immobilized 2-deoxy-2,3-didehydroneuraminic acid. The native sialidase has a molecular mass of 230 kDa (gel filtration) and consists of 4 subunits of each 63 kDa, as determined by SDS-gel electrophoresis. Its isoelectric point is at pH 4.9, the activity is optimum at pH 4.2 and 37 degrees C, and it hydrolyses preferably 4-methylumbelliferyl-alpha-N-acetyl-neuraminic acid, followed by sialyllactose and glycoproteins. The hydrolysis rate is decreased or stopped by the presence of O-acetyl groups on the sialic-acid residue to be cleaved. N-Glycoloyl residues also retard enzyme action, as well as alpha(2-6) bonds when compared with alpha(2-3) linkages. This relatively stable enzyme is inhibited by mercury or copper ions, 2-deoxy-2,3-didehydro-N-acetylneuraminic acid and by the increase of ionic strength. The evolutionary significance of starfish sialidase is discussed.
Schauer
R
R
Biochemisches Institut der Universität zu Kiel.
Wember
M
M
D000818:Animals; D002852:Chromatography, Ion Exchange; D002853:Chromatography, Liquid; D004591:Electrophoresis, Polyacrylamide Gel; D007525:Isoelectric Focusing; D007700:Kinetics; D008970:Molecular Weight; D009439:Neuraminidase / Q000032:analysis / Q000302:isolation & purification*; D011506:Proteins / Q000032:analysis; D013215:Starfish / Q000201:enzymology*
D011506:Proteins; D009439:Neuraminidase