Abstract
KURIYAMA, M., HIWATARI, R., OSAME, M. and IGATA, A. Leucocyte α-1, 4- and α-1, 6-Glucosidase Activities Towards Olggosaccharides in Late Onset Glycogenosis Type II. Tohoku J. Exp. Med., 1990, 161(4), 343-351-We describe the partial characterization and some properties of leucocyte α-glucosidase towards disaccharides with the α-1, 4 (maltose) and α-1, 6-glucosidic linkage (isomaltose) and tetrasaccharides with the α-1, 4 (maltotetraose) and α-1, 6-glucosidic linkage (tetrasaccharide, Glcα1→6Glcα1→4Glcα1→4Glc, which was isolated from the urine of a patient with glycogenosis type II). Leucocyte α-glucosidase showed optimal activity towards all four oligosaccharides under two conditions, acidic (pH 4.0-4.5) and neutral (pH 6.0-6.5) regions. Our comparative studies on enzyme kinetics showed that leucocyte α-glucosidase was able to hydrolyze both the 1→4 isomers and the 1→6 isomers at acidic and neutral pH. Acid α-glucosidase could hydrolyze maltose about 10 times faster than isomaltose, and maltotetraose about 5 times faster than tetrasaccharide isolated from urine. In leucocytes of the patient with late onset glycogenosis type II, acid α-glucosidase activities towards maltose, isomaltose, maltotetraose and tetrasaccharide isolated from urine showed 75.3%, 67.4%, 76.5% and 41.4% of normal control values, respectively. Neutral α-glucosidase activities towards these four oligosaccharides were normal. Tetrasaccharide with α-1, 6-glucosidic linkage might be accumulated by the impaired hydrolysis in the circulation as well as the leakage of undegraded glycogen to the circulation from the affected muscle.
