Е. V. Gudzenko, L. D. Varbanets
Zabolotny Institute of Microbiology and Virology, National Academy of Sciences of Ukraine, Kyiv;
The substrate specificity of Cryptococcus albidus and Eupenicillium erubescens ?-L-rhamnosidases has been investigated. It is shown that the enzymes are able to act on synthetic and natural substrates, such as naringin, neohesperidin. ?-L-Rhamnosidases hydrolysed the latter ones very efficiently, in this case E. erubescens enzyme was characterized by higher values of Vmax in comparison with the enzyme of C. albidus. However the C. albidus ?-L-rhamnosidase showed greater affinity for naringin and neohesperidin than the enzyme of E. erubescens (Km 0.77 and 3.3 mM and 5.0 and 3.0 mM, respectively). As regards the synthetic derivatives of monosaccharides, both enzymes exhibited narrow specificity for glycon: E. erubescens ?-L-rhamnosidase – only to the p-nitrophenyl-?-L-rhamnopiranoside (Km 1.0 mM, Vmax 120 µmol/min/mg protein), and C. albidus – to p-nitrophenyl-?-D-glucopyranoside (Km 10 mM, Vmax 5 µmol/min/mg protein). Thus, it was found that the enzyme preparations of E. erubescens and C. albidus are differed by their substrate specificity. The ability of E. erubescens and C. albidus ?-L-rhamnosidases to hydrolyse natural substrates: naringin and neohesperidin, evidences for their specificity for ?-1,2-linked L-rhamnose. Based on these data, we can predict the use of E. erubescens and C. albidus ?-L-rhamnosidases in various industries, food industry in particular. This is also confirmed by the fact that the investigated ?-L-rhamnosidases were stable at 20% concentration of ethanol and 500 mM glucose in the reaction mixture.
Key words: ?-L-rhamnosidase, Cryptococcus albidus, Eupenicillium erubescens, naringin, neohesperidin, substrate specificity, effect of glucose and ethanol on activation of ?-L-rhamnosidases.
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