초록
<P><B>Abstract</B></P> <P>A cellulolytic fungus YDJ216 was isolated from a compost and identified as an <I>Aspergillus</I> sp. strain. Two extracellular β-glucosidases, BGL1 and BGL2, were purified using ultrafiltration, ammonium sulfate fractionation, and High-Q chromatography. Molecular masses of BGL1 and BGL2 were estimated to be 97 and 45 kDa, respectively, by SDS-PAGE. The two enzymes eluted as one peak at 87 kDa by Sephacryl S-200 chromatography, and located at similar positions in a zymogram after intact gel electrophoresis, suggesting BGL1 and BGL2 might be monomeric and dimeric, respectively. Both enzymes showed similar enzymatic properties; they were optimally active at pH 4.0–4.5 and 60 °C, and had similar half-lives at 70 °C. Two enzymes also preferred <I>p</I>-nitrophenyl glucose (<I>p</I>NPG) with the same K<SUB>m</SUB> and hardly hydrolyzed cellobiose, suggesting both enzymes are aryl β-glucosidases. However, V<SUB>max</SUB> for <I>p</I>NPG of BGL1 (953.2 U/mg) was much higher than those of BGL2 (66.5U/mg) and other β-glucosidases reported. When tilianin (a flavone glycoside of acacetin) was reacted with both enzymes, inhibitory activity for monoamine oxidase, relating to oxidation of neurotransmitter amines, was increased closely to the degree obtained by acacetin. These results suggest that BGL1 and BGL2 could be used to hydrolyze flavone glycosides to improve their inhibitory activities.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Two extracellular aryl β-glucosidases, that is, BGL1 and BGL2, were purified from the isolate <I>Aspergillus</I> sp. YDJ216. </LI> <LI> BGL1 might be a monomeric form of 93 kDa, and BGL2 a dimeric form of 45 kDa polypeptides in their native forms. </LI> <LI> The <I>k</I> <SUB> <I>cat</I> </SUB> value of BGL1 for <I>p</I>NPG was much higher than those of BGL2 and previously reported β-glucosidases. </LI> <LI> BGL1 and BGL2 are able to effectively hydrolyze flavonoid glycosides. </LI> <LI> BGL1 and BGL2 can possibly be used to enhance the pharmaceutical inhibition of MAO enzymes. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>