Deletion analysis of the starch-binding domain of Aspergillus glucoamylase

Abstract

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The evolution of starch‐binding domain

“…With regard to the linker region connecting the other constitutive domains (especially the catalytic one) and an SBD, its length varies from a few to several tens of residues [15,17]. Although the SBD may behave as an independent structure‐functional module [18,21–23,39–41] with its own evolutionary history (this study), there should be a strong co‐operation between the SBD and the other constitutive domains (especially the catalytic one) via the linker region, as documented by studies with the glucoamylase from A. niger . It has been, for instance, revealed [42] that the C‐terminal part of the linker region has a destabilising effect on the catalytic domain, i.e.…”

“…The SBD motif, consisting of several β‐strand segments forming an open‐sided, distorted β‐barrel structure [17,18], is responsible for the ability of an amylase to bind and digest the native raw, granular starch [19,20]. In α‐amylases the SBD may govern the enzyme thermostability [21], however, this motif seems to have nothing to do with thermostability in glucoamylases [22]. It has been demonstrated [23] that the SBD independently retains its function even if fused to a protein other than amylase.…”

Starch-binding domains in the post-genome era

“…Trp 563 in A. niger glucoamylase) is essential for digestion of raw starch, whereas the sequence around Trp 589 (Trp 590 ) contributes to the adsorption to raw starch [49]. Chen et al [50] studied mutant glucoamylase from A. awamori containing extensive deletions at the C-terminus of or within the SBD. They concluded that any deletion mutations in SBD result in diminution or loss of raw starch binding and digesting ability of the glucoamylase [50].…”

“…Chen et al [50] studied mutant glucoamylase from A. awamori containing extensive deletions at the C-terminus of or within the SBD. They concluded that any deletion mutations in SBD result in diminution or loss of raw starch binding and digesting ability of the glucoamylase [50]. Using a similar approach with the α-amylase from Bacillus sp.…”

Cyclodextrin production and genetic characterization of cyclodextrin glucanotranferase of Paenibacillus graminis

“…The four conserved domains found in the CGTase of P. graminis translated sequence consisted of an alpha amylase catalytic (alpha-amyl, CDD:79479) domain and a C-terminus (Aamy_C, CDD:47909) domain, followed by a CGTase C-terminus domain (CGTase_C_t, CDD:30336) and a carbohydrate-binding Module-20 domain (CBM_ 20,CDD:79679). This last domain (conserved region of 90-130 amino acid residues) is shared by several amylolytic enzymes, acting on polysaccharides more rapidly than on oligosaccharides (Chen et al 1995).…”