1989 Volume 53 Issue 1 Pages 143-149
The enzymatically inactive but raw-starch-adsorbable glycopeptide-I (Gp-I), which was obtained from raw-starch-adsorbable, raw-starch-digesting glucoamylase I (GA I) of Aspergillus awamori var. kawachi as a result of proteolysis with subtilisin and proved to contain the raw-starch-affinity site essential for raw-starch-digestion, was found to promote the digestion rate of raw corn starch with GA I, maximally to the extent of 2.5 times. The raw-starch-adsorbability of Gp-I was decreased by the partial removal of carbohydrate moiety from Gp-I. The carbohydrate-split GA I could hydrolyze gelatinized substrates almost at the same rate as the native one, but significantly decreased in the adsorbability and digestibility onto raw starch in comparison with the original one. From the function and the characteristic structure of the parallel short mannoside chains linked to the successive sequence of hydroxy amino acid residues of Gp-I, the "water-cluster-dissociating model" for the hypothetical mechanism of raw-starch-digestion by the adsorption of GA I at the affinity site onto starch was proposed.
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