Abstract
We analyzed the functional structure of Streptococcus bovis 148 α-amylase (AmyA) to determine the starch binding domain (SBD) of this enzyme. Several derivative AmyAs and putative SBD segments were constructed and assayed their adsorption ability onto raw starch. On the basis of the results, a putative linker domain region and two SBDs (SBDα and SBDβ) were found at the C-terminal region of AmyA. SBDα and SBDβ showed 56% amino acid sequence similarity; these SBDs were considered to be tandem repeat motif. In addition, we constructed a chimeric enzyme CsaB, which consisted of S. bovis 148 irresolvable intracellular α-amylase (AmyB) as for insoluble starch and a putative linker plus two SBDs. This enzyme succeeded in conferring starch adsorption and hydrolysis abilities, which suggests that SBD reacts with the surface of raw starch and breaks down its structure.
