The influence of selected O-alkyl derivatives of cyclodextrins on the enzymatic decomposition of L-tryptophan by L-tryptophan indole-lyase

摘要

A series of 0-alkyl derivatives of cyclodextrin: heksakis[2,3,6-tri-0-(2'-methoxyethyl)]-a-cyclodextrin; heksakis(2,3-di-0-methyl)-a-cyclodextrin; heptakis(2,3-di-O-methyl)-β-cyclodextrin; heksakis[2,3-di-0_methyl-6-0-(2'-methoxyethyl)]-a.-cyclodextrin; heptakis[2,3-di-0-methyl-6-O-(2'-methoxyethyl)]-β-cyclodextrin; heksakis[2,3-di-0-(2'-methoxyethyl)]-a-cyclodextrin and heptakis[2,3-di-0-(2'-methoxy_ethyl)]-[3-cyclodextrin have been synthesized. Purity and composition of the obtained substances were examined. The cyclodextrin derivatives listed above as well as (2-hydroxypropyl)-a.-cyclodextrin and (2-hydroxypropyl)-_-cyclodextrin, the two commercially available ones, have been investigated as the additives in the course of enzymatic decomposition of L-tryptophan by L-tryptophan indole-lyase. It has been found that each of cyclodextrin derivatives causes the inhibition of enzymatic process, both competitive and non-competitive. The competitive inhibition is connected with the formation of inclusion complexes between cyclodextrins and L-tryptophan, related to the geometry of these complexes. The mechanism of the non-competitive inhibition is not so evident; it could be related to the formation of the cyclodextrin complexes on the surface of the enzyme, leading to the change in the flexibility of the enzyme molecule.