Activation of α-Amylase by Protein and Detergents1

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Abstract
Optimal salt concentration for α-amylase hydrolysis of the PHADEBAS starch substrate was 50 mmol/1 NaCl, and 50 mmol/1 phosphate buffer (pH 7.0). Under these conditions, 7 μmol/l albumin increased the activity of the enzyme 1.3-fold. The degree of activation was shown to depend on pH. Activation was greatest in the more acid region. At pH 5.4 with 7 μmol/1 albumin, there was a 6-fold increase in activity over the control. The degree of activation fell to 2-fold at pH 6.0. A similar trend in activation versus pH was shown with the bile salt sodium taurodeoxycholate, the neutral detergent Triton X-100 and the polymer polyethylene glycol. The degree of activation, however, was less than with protein. With 1.25 mmol/1 bile salt, the activation was 2.5-fold at pH 5.4, falling to 1.4-fold at pH 6.0. Albumin caused an increase in Vmax accompanied by an apparent decrease in K(m). With taurodeoxycholate, V(max) was increased without change in the apparent K(m). The possible mechanism of activation is discussed.

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