Identity of alpha-glucosidase of human kidney with urine F-1 alpha-glucosidase.

alpha-Glucosidase was extracted from a homogenate of human kidney, initially with 0.02 M Tris-HCl buffer, pH 7.6, and subsequently with a mixture of 0.5% cholate and 0.5% Triton X-100 in the same buffer, pH 7.6. The enzyme in each of these two fractions was purified to the electrophoretically pure state by fractional precipitation with ammonium sulfate, column chromatographies on DEAE-cellulose, hydroxyapatite, Bio Gel A-1.5 m and affinity chromatography on heated glutinous rice. The two purified alpha-glucosidase preparations obtained were the same in enzymatic and proteochemical properties, and the molecular weight and isoelectric point estimated were 3 x 10(5) and 4.2, respectively. No evidence for subunit structure was obtained. The optimum pH for activity was 5.6 and the activity was drastically inhibited by Nojirimycin. The alpha-glucosidase readily hydrolyzed maltose, starch, and glycogen, producing only glucose. It hydrolyzed maltotriitol to split the non-reducing end glucose, but scarcely hydrolyzed maltitol or various other heteroglucosides examined. All these proteochemical and enzymatic properties of kidney alpha-glucosidase were the same as those of urine F-1 alpha-glucosidase. Also, kidney tissue alpha-glucosidase produced a clear precipitin line with antisera against urine F-1 alpha-glucosidase. These facts suggest that F-1 alpha-glucosidase in urine originates from kidney tissue.