Glycobiology Advance Access originally published online on October 13, 2004
Glycobiology 2005 15(3):211-220; doi:10.1093/glycob/cwi006
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Glycobiology vol. 15 no. 3 © Oxford University Press 2005; all rights reserved.
Sequencing, expression, and enzymatic characterization of ß-hexosaminidase in rabbit lacrimal gland and primary cultured acinar cells
Department of Chemistry and Biomedical Sciences, University of Kalmar, SE- 391 82 Kalmar, Sweden
1 To whom correspondence should be addressed; e-mail: peter.gierow{at}hik.se
Received on June 16, 2004; revised on October 9, 2004; accepted on October 11, 2004
The lysosomal enzyme, ß-hexosaminidase, exists as two major isoforms; HexA and HexB. HexA is an 
ß-subunit heterodimer and HexB a ß-subunit homodimer. Both isoforms can remove nonreducing ß-N-acetyl-D-glucosamine residues, whereas HexA hydrolyzes charged substrates as GM2 gangliosides as well. ß-Hexosaminidase is present in both human and rabbit tear fluid and is secreted from rabbit lacrimal gland acinar cells in primary culture on stimulation with secretagogs. To further characterize the enzyme, the - and ß-subunit mRNA expression was explored in rabbit lacrimal gland tissue as well as in cultured cells. Possible correlation between mRNA expression and HexA specific enzymatic activity was also investigated. Because existing ß-hexosaminidase antibodies are unable to recognize the rabbit enzyme, cloning and sequencing of the - and ß-subunits were performed. Sequencing of the these subunits indicate that both are highly conserved between human, mouse, and rabbit. In contrast to the ß-subunit, showing an even mRNA expression between tissue and cultured cells, the level of -subunit expression was higher in cultured acinar cells compared to tissue, with no alteration after cell stimulation. A minor but significant increase in total ß-hexosaminidase as well as HexA activity was observed in cultured cells compared to tissue. Enzymatic activity assays also revealed that HexA is the dominating isoform of ß-hexosaminidase in lacrimal gland and cultured acinar cells.
Key words: enzyme activity / expression / ß-hexosaminidase / lacrimal gland / sequencing
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