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

Abstract

A series of O-alkyl derivatives of cyclodextrin: heksakis[2,3,6-tri- O-(2′-methoxyethyl)]-α-cyclodextrin; heksakis(2,3-di- O-methyl)-α-cyclodextrin; heptakis(2,3-di- O-methyl)-β-cyclodextrin; heksakis[2,3-di- O-methyl-6- O-(2′-methoxyethyl)]-α-cyclodextrin; heptakis[2,3-di- O-methyl-6- O-(2′-methoxyethyl)]-β-cyclodextrin; heksakis[2,3-di- O-(2′-methoxyethyl)]-α-cyclodextrin and heptakis[2,3-di- O-(2′-methoxyethyl)]-β-cyclodextrin have been synthesized. Purity and composition of the obtained substances were examined. The cyclodextrin derivatives listed above as well as (2-hydroxypropyl)-α-cyclodextrin and (2-hydroxypropyl)-β-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.