Four molecular forms of α-glucosidase were isolated from spinach seeds by several kinds of chromatography. The molecular masses of α-glucosidases I, II, III, and IV were 78, 78, 82, and 82kDa by SDS-PAGE, and 62, 62, 190, and 70kDa by gel filtration, respectively. α-Glucosidases I and II showed similar enzymatic properties, in which the Km for soluble starch was about 10 times lower than that for maltose, and they had higher activity not only toward malto-oliosaccharides but also toward α-glucans. The optimum pH was 4.5-5.5 and about 50% of the activity remained after incubation at 70°C for 20min. On the other hand, α-glucosidases III and IV showed similar enzymatic properties, in which the Km for maltose was 3-4 times lower than that for soluble starch, and they had high activity toward malto-oligosaccharides but faint activity toward α-glucans. The optimum pH was 4.5-5.0 and no activity was found after incubation at 70°C for 20min. However, anti-α-glucosidase III serum formed precipitation specifically with α-glucosidase III.
ASJC Scopus subject areas
- Analytical Chemistry
- Applied Microbiology and Biotechnology
- Molecular Biology
- Organic Chemistry