[Catalytic properties of a neutral alpha-glucosidase from human kidney]

The catalytic properties of a neutral alpha-glucosidase purified to homogeneity from human renal cortex are described. The pH optimum was 6 (maltose and starch). It has a broad range of substrate specificity, hydrolysing di- and oligosaccharides with alpha (1 leads to 2), alpha (1 leads to 3), alpha (1 leads to 4) and alpha (1 leads to 6) linkages. Glucosidase action on maltosaccharides was associated with pronounced substrate inhibition at concentrations exceeding 0,5 mM. It also hydrolyses polysaccharides as starch and glycogen. The Km and Vmax values for the various substrates were determined. The enzymes exhibited intrinsic transglucosylase activity. It catalysed glucosyl-transfer reaction from maltose to itself (disproportionation). Mixed substrate inhibition studies, inhibition studies and heat inactivation are interpreted in terms of the existence of at least two interacting sites on the enzyme.