Evaluation on the hydrolysis of methylumbelliferyl-tetra-N-acetylchitotetraoside by various glucosidases. A comparative study.
1. In human plasma, an enzyme is present which hydrolyzes 4-methylumbelliferyl-tetra-N-acetylchitotetraoside. The function of this enzyme is unknown. 2. We have examined whether hyaluronidase, neutral endoglucosaminidase, N-acetyl-beta-D-hexosaminidase, aspartylglucosaminidase, beta-D-glucosidase, and chitobiase could hydrolyze MU-TACT. The results obtained are detailed below. 3. A purified commercial preparation of hyaluronidase does not hydrolyze MU-TACT. 4. Substrate specificity requirements, pH optimum and subcellular localization indicate that neutral endoglucosaminidase is distinguishable from MU-TACT hydrolase. Also commercial neutral endoglucosaminidase D and H have no affinity towards MU-TACT. 5. N-Acetyl-beta-D-hexosaminidase is different from MU-TACT hydrolase for the following reasons: (a) a purified enzyme preparation does not hydrolyze MU-TACT; (b) there is no correlation in the activity of the enzymes; (c) MU-TACT hydrolase is not deficient in cells of a patient with a deficiency of total N-acetyl-beta-D-glucosaminidase; and (d) the 2 enzymes have very different chromatographic characteristics and Con A binding properties. 6. Enzyme characteristics, substrate structural requirements and a lack of correlation with MU-TACT hydrolase activity suggest that aspartylglucosaminidase, beta-D-glucosidase, and chitobiase are not involved in the hydrolysis of MU-TACT. 7. None of the enzymes which we have considered corresponds to MU-TACT hydrolase. The exact nature and the function of the enzyme remains an enigma.
Den Tandt
W R
WR
Faculty of Medicine, University of Antwerp, Wilrijk, Belgium.
Scharpe
S
S
Overdijk
B
B
D000818:Animals; D002240:Carbohydrate Sequence; D002458:Cell Fractionation; D002478:Cells, Cultured; D005260:Female; D005959:Glucosidases / Q000037:antagonists & inhibitors / Q000097:blood / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D006923:Hymecromone / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors / Q000378:metabolism; D008099:Liver / Q000201:enzymology; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D012497:Sandhoff Disease / Q000201:enzymology
C027049:4-methylumbelliferyl-N-acetylchitotetraoside; D009844:Oligosaccharides; D006923:Hymecromone; D005959:Glucosidases