title: alpha-mannosidase involved in turnover of plant complex type N-glycans in tomato (Lycopersicum esculentum) fruits.
abstract: In this study, we purified and characterized an alpha-mannosidase to homogeneity from mature red tomato fruits. Purified alpha-mannosidase (alpha-Man LE-1) gave two separate bands, of molecular masses of 70 kDa (L-subunit) and 47 kDa (S-subunit), on SDS-PAGE under non-reducing and reducing conditions. On the other hand, the molecular weight was estimated to be 230 kDa by gel filtration, indicating that alpha-Man LE-1 functions in a tetrameric structure in plant cells. The N-terminal sequence of the L-subunit and the S-subunit were determined to be L-Y-M-V-Y-M-T-K-Q-G- and X-X-L-E-Q/K-S-F-S-Y-Y respectively. When pyridylaminated N-glycans were used as substrates, alpha-Man LE-1 showed optimum activity at about pH 6 and at 40 degrees C, and the activity was completely inhibited by both swainsonine and 1-deoxy-mannojirimycin. alpha-Man LE-1 hydrolyzed the alpha-mannosidic linkages from both high-mannose type and plant complex type N-glycan, but preferred a truncated plant complex type structure to high-mannose type N-glycans bearing alpha1-2 mannosyl residues.
authors.affiliation: Department of Biofunctional Chemistry, Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan.
authors.forename: Md Anowar
authors.initials: MA
authors.lastname: Hossain
authors.forename: Kosuke
authors.initials: K
authors.lastname: Nakamura
authors.forename: Yoshinobu
authors.initials: Y
authors.lastname: Kimura
mesh_terms: D000595:Amino Acid Sequence; D007700:Kinetics; D018551:Solanum lycopersicum / Q000737:chemistry*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011134:Polysaccharides / Q000378:metabolism*; D043323:alpha-Mannosidase / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D011134:Polysaccharides; D043323:alpha-Mannosidase