Research of regularities for process of the thermal inactivation of the immobilized inulinase from Helianthus tuberosus

Abstract

Inulinases (EC 3.2.1.7) participate in a carbohydrate metabolism of the higher plants and
microorganisms. They can be used in cycles of sugars production with various extent of polymerization, in
particular, of inulin, fructose and inulooligo-saccharides. Heat stability is the major selection criterion for
enzymes of industrial value therefore research of regularities a thermal inactivation process of the inulinase
from Helianthus tuberosus immobilized on KU-2 was the purpose of this work.
The fractions of protein from Helianthus tuberosus tubers with inulinase activity, immobilized on
ion-exchange KU-2 pitch, were objects of research (activity of heterogeneous preparation was ~ 80%).
Protein content was determined by Lowry method, catalytic activity of enzyme was measured by rezortsin
method.
It is established that at 50 and 60 °C the incubation of an inulinase doesn't lead to saltatory changes
in catalytic activity of a preparation, enzyme is inactivated gradually, keeping respectively 84% and 81% of
Холявка и др. / Сорбционные и хроматографические процессы. 2015. Т. 15. Вып. 2
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catalytic ability at 60-minute warming up of samples. After 40 minutes of incubation at 70 °C sharp
reduction of catalytic activity of a sample, which decreases to 40% at 60-minute warming up, is observed. At
80 °C process of an inactivation happens more intensively and after 60 minutes only 15% of preparation
activity remain. High loss of catalytic ability is carried out at 90 °C: after 10 minutes of enzyme incubation in
buffer solution the percent of activity preservation makes 59%, and after 60 minutes there are only 7% of
initial activity were.
Despite distinction in the regularities of course for process of a thermal inactivation of immobilized
inulinases from fungi and plants, adsorption on ion-exchange pitches and fibers not only allows to increase
value of a temperature optimum of their functioning, stabilizes conformation of molecules, but also protects
spatial structure of enzymes, increasing heat stability of preparations. The adsorptive enzyme becomes stable
in relation to denaturant factors of environment that expands the horizons of its application in the
pharmaceutical, food industry, and in analytical practice.