Studies on the aroma formation mechanism in oolong tea .5. Isolation and characterization of a beta-primeverosidase concerned with alcoholic aroma formation in tea leaves

A beta-primeverosidase concerned with alcoholic aroma formation during tea processing was purified from cv. Yabukita (Camellia sinensis var. sinensis). The acetone powder was subjected to ammonium sulfate precipitation and then to chromatographic purification with CM-Toyopearl 650M to give three active fractions, Glucosidases (Gls)-I, II, and III fractions. The main GI-II fraction was characterized as a beta-primeverosidase, which hydrolyzed a beta-primeveroside into an aglycone and a primeverose (6-O-beta-D-xylopyranosyl-beta-D-glucopyranose) and was mainly concerned with alcoholic tea aroma formation. The GI-II fraction was further seperated into Gls-IIa (main) and IIb (minor) by ion-exchange Mono S column chromatography. GI-IIa was determined to be a monomeric protein of 61 kDa with pI 9.4. GI-IIa was stable at temperature lower than 45 degrees C and at between pH 5 and 7, and showed its highest activity at 50 degrees C and at pH 5.