抄録
The raw-starch-affinity site of Aspergillus awamori var. kawachi glucoamylase I (GAI), that was proved to be essential for its adsorbability and digestibility on raw starch granules, was found to be located separately from the active site in the region corresponding to glycopeptide I (Gp-I) liberated from the glucoamylase I through the action of subtilisin. Gp-I consists of 45 amino acid residues, hydroxy amino acids being characteristically abundant, and 56 mannose residues. The sequence was determined with an automatic amino acid sequencer to be ATGGTTTTATTTGSGGVTST SKTTTTASKTSTTTSSTSCTTPTAV. A structure of parallelly arranged short mannoside chains linked o-glycosidically to the successive sequence of hydroxy amino acid residues on Gp-I was revealed. On comparison of the amino acid sequence of Gp-I with those of three glucoamylases, from Aspergillus awamori, Aspergillus niger and Rhizopus oryzae, significantly homologous regions (91%, 91% and 77% homology, respectively) were detected as the affinity site that could be functionally constrained and essential for raw-starch-digesting glucoamylase.
