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The aim of this work was the study of native and galactosidases from Penicillium canescens under denaturing conditions caused by guanidine hydrochloride. Calculation of kinetics and constants of enzymes inactivation was carried out on using experimental kinetic curves of enzyme denaturation. We observed significant differences in the kinetics of inactivation of native and deglycosylated α-galactosidases from P. canescens caused by guanidine hydrochloride. Native enzyme was stable within the selected range of guanidine hydrochloride concentrations (from 0.1 to 3.0 M), retaining no less than 50% of the initial enzyme activity for 3 days. Deglycosylated enzyme preparations were less stable and they lost their activity within 5–30 minutes, when they were treated with guanidine hydrochloride in concentrations above 1 M. Dissociation rate constant of native and deglycosylated forms of the enzyme differed by 10 to 100 folds. It was shown that subunit interactions play a major role in the process of inactivation of the enzyme, and the carbohydrate component is essential for stabilizing of subunit bonds and maintaining conformational stability of the enzyme under denaturing conditions of chemical agents.

One of the important problems of current biotechnology is the usage of enzymes of microbial origin for destruction of poorly soluble compounds and synthesis of new drugs. In recent years a great deal of researchers’ attention has been given to such technologically promising carbohydrases as O-glycosylhydrolases catalyzing the hydrolysis of O-glycoside links in glycosides, oligo- and polysaccharides, glycolipids, and other glycoconjugates. Aim. The review provides data on the position of α-L-rhamnosidases in the modern hierarchical classification of glycosidases and presents data available in the literature on the features of the enzyme structure in various microorganisms. Methods. The publications from the following databases were analyzed: PubMed (https://pubmed. nsbi.nlm.nih.gov/), the Carbohydrate-Active enZYmes (http://www.cazy.org/), the BRENDA Enzyme Database (https://www.brenda-enzymes.org/). Results. Data on the physicochemical, catalytic, and kinetic properties of α-L-rhamnosidases in microorganisms of different taxonomic groups have been systematized. The peculiarities of the substrate specificity of the enzyme depending on the nature of the protein and the growing conditions of the producer are characterized. Conclusions. Functional properties and specificity action of microbial α-L-rhamnosidases suggest their broad-range applicability for food and animal feed processing, as well as obtaining biologically active compounds for the pharmaceutical industry and medicine. [ABSTRACT FROM AUTHOR]

The aim of the work was to investigate the practical using of α-L-rhamnosidase substrate specificity Cryptococcus albidus. p-Nitrophenyl derivatives of monosaccharides were used to determine the activity and the enzyme specificity. The ability to hydrolyze of natural substrates was evaluated by Davis and high-performance liquid chromatography methods. It was shown that the enzyme exhibited narrow specificity towards the glycon of synthetic substrates and hydrolyzes only p-nitrophenyl-α-Lrhamnopyranoside (Km 4.5 mM) and p-nitrophenyl-α-D-glucopyranoside (Km 10.0 mM). C. albidus α-Lrhamnosidase the most active degrades naringin (Km 0.77 mM), releasing prunin and naringenin. Km for neohesperidin was 3.3 mM. The efficacy of the naringin hydrolysis in grapefruit and pomelo juice was 98 and 94% in 60 min (40 °C, 2 U/ml). As the result of of green tea and orange juice treatment by α-Lrhamnosidase, there was a decrease in the content of rutin, narirutin and hesperidin, indicating that α-1,2-and α-1,6-linked rhamnose could be cleaved from natural flavonoids. The study shows the possibility of citrus juices and green tea treatment by C. albidus α-L-rhamnosidase for the purpose of their taste qualities improvment and obtaining bioavailable flavonoids glucosides. [ABSTRACT FROM AUTHOR]

The aim of the research was a comparative study of the thermal stability of native and modified by various methods α-L rhamnosidases of Eupenicillium erubescens and Cryptococcus albidus for improving the stability of enzymes. Denaturation of native and modified enzymes were performed at 65 0C, pH 5.2. Enzyme activity was determined using p-nitrophenyl-α-L-rhamnopyranoside and naringin. It is found that in the treatment by polyethylenglycol PEG 1500, dextrans 500 and 70 T thermostability of α-L-rhamnosidases tested decreases, while modification with polyethylenglycol 20000 leads to increase thermal stability of the E. erubescens enzyme to 280% and C. albidus to 150%. Comparative study of the thermal stability of the native and modified by cellulose and its derivatives α-L-rhamnosidases of C. albidus and E. erubescens showed that at concentrations cellulose of 5-15 μg/10 μg protein protective effect of polymers on enzymes was investigated was observed. Hydrophobic modifications using succinic anhydride also can slow down the denaturation of α-L-rhamnosidases tested under experimental conditions. These stabilized C. albidus and E. erubescens α-L-rhamnosidases can be used in biotechnological processes. [ABSTRACT FROM AUTHOR]

The study of the features of thermal inactivation of α-L-rhamnosidase from Eupenicillium erubescens aiming to develop further strategies for improving the stability of the enzyme was the purpose of the research. Two forms of α-L-rhamnosidase were studied. They were obtained by producer cultivation on two different carbon sources (rhamnose and naringin). It was shown that at temperatures above 60°C heat inactivation process is described by the first order reaction kinetics. It was established that stability of α-Lrhamnosidase from E. erubescen, grown on naringin depends on hydrophobic interactions rather than electrostatic ones. It was shown that aggregation of enzyme molecules could lead to their thermal stabilization. The important role of cysteine residues and possible involvement of the metal cation in maintaining of active form of α-L-rhamnosidases from E. erubescens was highlighted. [ABSTRACT FROM AUTHOR]