Characterization of a soluble class I alpha-mannosidase in human serum.
Class I alpha-mannosidases are thought to exist exclusively as integral membrane proteins that play intracellulary an essential role in the N-glycan biosynthesis. Using [3H]Man9GlcNAc2 as a substrate, we were able to identify a soluble alpha-mannosidase in human serum that trims the substrate Man9GlcNAc2 to Man(5-8)GlcNAc2 with Man6GlcNAc2 being the major product. This serum mannosidase is Ca2+-dependent, sensitive to 1-deoxymannojirimycin but insensitive to the class II inhibitor swainsonine and, hence, belongs to class I mannosidases. The enzymatic properties of the serum class I mannosidase are similar to that of the membrane bound class I mannosidases Golgi-mannosidase IA and IB and Man9-mannosidase.
Porwoll
S
S
Institut für Laboratoriumsmedizin und Pathobiochemie, Medizinische Fakultät Charité der Humboldt-Universität zu Berlin, Campus Virchow-Klinikum, Germany.
Fuchs
H
H
Tauber
R
R
D006801:Humans; D007700:Kinetics; D008361:Mannosidases / Q000097:blood* / Q000378:metabolism; D012995:Solubility; D014407:Tumor Cells, Cultured; D043323:alpha-Mannosidase
D008361:Mannosidases; D043323:alpha-Mannosidase