Tag Archives: naringin
Substrate specificity of Cryptococcus albidus and Eupenicillium erubescens α-L-rhamnosidases
Е. V. Gudzenko, L. D. Varbanets
Zabolotny Institute of Microbiology and Virology, National Academy of Sciences of Ukraine, Kyiv;
е-mail: varbanets@serv.imv.kiev.ua
The substrate specificity of Cryptococcus albidus and Eupenicillium erubescens α-L-rhamnosidases has been investigated. It is shown that the enzymes are able to act on synthetic and natural substrates, such as naringin, neohesperidin. α-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 α-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 α-L-rhamnosidase – only to the p-nitrophenyl-α-L-rhamnopiranoside (Km 1.0 mM, Vmax 120 µmol/min/mg protein), and C. albidus – to p-nitrophenyl-α-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 α-L-rhamnosidases to hydrolyse natural substrates: naringin and neohesperidin, evidences for their specificity for α-1,2-linked L-rhamnose. Based on these data, we can predict the use of E. erubescens and C. albidus α-L-rhamnosidases in various industries, food industry in particular. This is also confirmed by the fact that the investigated α-L-rhamnosidases were stable at 20% concentration of ethanol and 500 mM glucose in the reaction mixture.
Thermal stability of Cryptococcus albidus α-L-rhamnosidase
O. V. Gudzenko, N. V. Borzova, L. D. Varbanets
Zabolotny Institute of Microbiology and Virology,
National Academy of Sciences of Ukraine, Kyiv, Ukraine;
e-mail: nv_borzova@bigmir.net
Yeast as well as micromycetes α-L-rhamnosidases, currently, are the most promising group of enzymes. Improving of the thermal stability of the enzyme preparation are especially important studies. Increase in stability and efficiency of substrate hydrolysis by α-L-rhamnosidase will improve the production technology of juices and wines. The aim of our study was to investigate the rate of naringin hydrolysis by α-L-rhamnosidase from Cryptococcus albidus, and also some aspects of the thermal denaturation and stabilization of this enzyme. We investigated two forms of α-L-rhamnosidase from C. albidus, which were obtained by cultivation of the producer on two carbon sources – naringin and rhamnose. A comparative study of properties and the process of thermal inactivation of α-L-rhamnosidases showed that the inducer of synthesis had no effect on the efficiency of naringin hydrolysis by the enzyme, but modified thermal stability of the protein molecule. Hydrophobic interactions and the cysteine residues are involved in maintaining of active conformation of the α-L-rhamnosidase molecule. Yeast α-L-rhamnosidase is also stabilized by 0.5% bovine serum albumin and 0.25% glutaraldehyde.