The radius of gyration of α-amylase is 26.9 Å, as found by means of small angle X-ray scattering. This value decreases by 0.5 Å if amylase binds three moles ofβ-cyclodextrin per mole enzyme.
In case of partial saturation, the solution contains only saturated amylase-cyclodextrin complexes (amylase/cyclodextrin molar ratio 1:3) and amylase molecules free of cyclodextrin. The binding of β-cyclodextrin follows the all-or-none mechanism.
The specifically bound β-cyclodextrin molecules are accommodated in a trough of the amylase molecule. The plane of bound cyclodextrin is perpendicular to the longitudinal axis of the trough. It is suggested that the helical substrate, amylose, binds in this trough, too.
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Simon, I., Móra, S. & Elödi, P. Studies on the active center of pancreatic amylase. Mol Cell Biochem 4, 211–216 (1974). https://doi.org/10.1007/BF01731483
- Active Center
- Small Angle