Function of conserved tryptophans in the Aspergillus niger glucoamylase 1 starch binding domain

A study followed a binding site numbering convention developed in previous research in domain E of cyclodextrin glycosyltransferase to determine the function of several tryptophan residues in the granular starch binding domain (SBD) of Aspergillus niger glucoamylase I. Findings show that the binding site 2 of SBD has a significantly higher affinity for the ligand than site. It appears that site 1 acts as the initial recognition site while site 2 is more involved in pre[paring the substrate for catalysis.