Germanium (IV) Complexes with Gluconic Acid as Effectors of Penicillium tardum and Eupenicillium erubescens α-L-Rhamnosidases

Abstract

α-L-Rhamnosidase (α-L-rhamnoside-rhamnohydrolase EC 3.2.1.40) showing specificity for terminal α-1,2-, α-1,4- and α-1,6-linked rhamnose residues, which often present in glycoconjugates and synthetic glycosides, can be successfully used in biotechnology for the hydrolysis of rhamnopyranoside residues present in some bioflavonoids, glycoproteins, glycolipids, and other glycoconjugates. Previously, we have shown that a significant part of the coordination compounds of various metals act as effectors of the activity of α-L-rhamnosidases. The aim of this investigation was to study the effect of a number of newly synthesized coordination compounds of Ge(IV) and Ba(II), (Co(II), Ni(II), Cu(II), Zn(II) with gluconic acid on the activity of Penicillium tardum and Eupenicillium erubescens α-L-rhamnosidases. Methods. The objects of the study were Penicillium tardum and Eupenicillium erubescens α-L-rhamnosidases. α-L-Rhamnosidase activity was determined by the Davis method using naringin as a substrate. Coordination compounds Ge(IV) and Ba(II), Co(II), Ni(II), Cu(II) ,and Zn(II) with gluconic acid were used as enzyme activity modifiers. The synthesized complexes correspond to the formulas [М(H2O)6][Ge2(OH)2(C6H8O7)2]·nH2O (М = Ba(1), n=2; Co(2), n=4; Ni(3), n=4; Cu(4), n=4; Zn(5), n=3). Results. The effect of coordination compounds 1-(5) on the activity of α-L-rhamnosidase in two strains of Penicillium tardum and Eupenicillium erubescens was studied depending on the exposure time and concentration of the effector. It was shown that compound (3) at a concentration of 0.01% (1 h incubation) led to a slight (by 5%) increase in the activity of P. tardum α-L-rhamnosidase. Compound 1 at a concentration of 0.1% led to a decrease in the activity of P. tardum α-L-rhamnosidase by 29% during the first hour, and after 24 h of incubation, a decrease in the inhibitory effect to 15% was noted. Compounds 2 and (4) activated the enzyme by 9-39% at 1h exposure. At a concentration of 0.1% and exposure time of 1 h, compound 1 increased the activity of E. erubescens α-L-rhamnosidase by 80%, while at a decrease in concentration to 0.01%, the activity increased only by 29%. In general, it should be noted that in most cases, an increase in the duration of incubation up to 24 h led to a decrease in the level of activation (or inhibition) and a return to the control values of enzyme activity. Conclusions. The variety of effects of metal coordination compounds on the activity of enzymes, depending on the nature of the cation and the origin of the enzyme, has been established. The involvement of Ba(II) had the greatest activating effect on the activity of E. erubescens α-L-rhamnosidase compared to other metals.