Glycobiology Advance Access published online on October 13, 2004
Glycobiology, doi:10.1093/glycob/cwi006
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1 Department of Chemistry and Biomedical Sciences, University of Kalmar, SE-391 82 Kalmar, Sweden
* To whom correspondence should be addressed. E-mail: peter.gierow{at}hik.se.
The lysosomal enzyme,
Revised October 9, 2004
Accepted October 11, 2004
ORIGINAL ARTICLES
Sequencing, expression and enzymatic characterization of
-hexosaminidase in rabbit lacrimal gland and primary cultured acinar cells
Abstract 
-hexosaminidase, exists as two major isoforms; HexA and HexB. HexA is an 
-subunit heterodimer and HexB a -subunit homodimer. Both isoforms can remove non-reducing -N-acetyl-D-glucosamine residues, whereas HexA hydrolyses charged substrates as GM2 gangliosides as well. -hexosaminidase is present in both human and rabbit tear fluid and is secreted from rabbit lacrimal gland acinar cells in primary culture upon stimulation with secretagogues. In order to further characterize the enzyme, the - and -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. Since existing -hexosaminidase antibodies are unable to recognize the rabbit enzyme, cloning and sequencing of the - and -subunits were performed. Sequencing of the -and -subunits indicate that both subunits are highly conserved between human, mouse and rabbit. In contrast to the -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 -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 -hexosaminidase in lacrimal gland and culture acinar cells.-hexosaminidase; Enzyme activity.
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