Two forms of the lysosomal enzyme β-mannosidase were identified and purified from human urine. The purification strategy employed allowed sufficient quantities of both forms to be obtained for subunit analysis and for further characterizations. The two β-mannosidases were identified as β-mannosidase B and A, in order of their elution from an ion-exchange column. In all samples examined, the A form was predominant, and the B/A ratio was consistently 0.14. The two forms displayed the same optimum pH (i.e., 4.3) and both were retained by a Concanavalin-A Sepharose column, but showed different isoelectric points, molecular masses and subunit compositions. Native- and sodium dodecyl sulfate-polyacrylamide gel electrophoresis analyses of pure β-mannosidases B and A suggest that active protein B (160 kDa) consists of three subunits, one 75 kDa and two 49 kDa subunits. Protein A is smaller and appears to be composed of three subunits of 75 kDa, 49 kDa and 37 kDa. Two forms of β-mannosidase, exhibiting a chromatographic behaviour comparable to the urinary farms, were also detected in human kidney. Nevertheless, in this tissue their relative distribution was different, the B/A ratio being 19.
|Number of pages||8|
|Journal||Biochimica et Biophysica Acta (BBA)/Protein Structure and Molecular|
|Publication status||Published - Mar 7 1996|
ASJC Scopus subject areas
- Molecular Biology
- Structural Biology