Abstract
The number of exposed tryptophan residues in bacterial saccharifying α-amylase was estimated by the solvent perturbation technique using several perturbants. Five to six of the eleven residues were found to be exposed.
A difference spectrum of the enzyme, attributable to one tryptophan residue, was found to be produced by addition of cycloheptaamylose.
The Michaelis constant, Km and the molecular activity, k0 for hydrolysis of cycloheptaamylose by the enzyme were determined at pH 5.4 and 25°C. The Km value is slightly larger than that for maltotriose but considerably smaller than that for maltose, suggesting that the binding of cycloheptaamylose involves nearly three subsites.
These results indicate that one of the five to six exposed tryptophan residues of the enzyme is located in one of the three subsites and is responsible for the difference spectrum produced upon binding of cycloheptaamylose.
