Kinetic Studies on the Hydrolyses of α-, β-, and γ-Cyclodextrins by Taka-amylase A

抄録

1) Hydrolyses of α-, β-, and γ-cyclodextrins catalyzed by Taka-amylase A^*3 [EC 3. 2. 1. 1] were studied at pH 5.3 and 25°C.
2) The rate parameters, Michealis constant K_m and molecular activity κ₀ for the cleavage of the cyclodextrin ring, were determined for the three cyclodextrins by using glucoamylase^*4 [EC 3. 2. 1. 3] in the analytical procedure to discriminate ring cleavage from the subsequent hydrolysis of chain product. It was found that the κ₀ value increased markedly in the order α-, β-, and γ-cyclodextrins, but the K_m values did not differ to any great extent among the three cyclodextrins.
3) By using glucoamylase, it was shown that the multiple attack mechanism was operative in the hydrolysis of cyclodextrins by this enzyme, and the degree of multiple attack was estimated to be 1.5±0.1, irrespective of the kind of cyclodextrin.