Purification of a β-Primeverosidase Concerned with Alcoholic Aroma Formation in Tea Leaves (Cv. Shuixian) To Be Processed to Oolong Tea

Abstract

β-Primeverosidase, which is concerned with the alcoholic aroma formation in tea leaves, was purified from fresh tea leaves (Camellia sinensis var. sinensis cv. Shuixian) to be processed to oolong tea by successive precipitation with acetone and ammonium sulfate followed by column chromatography on CM-Toyopearl and Mono S-HR. The molecular mass was shown to be 61 and 60.3 kDa by SDS−PAGE and TOFMS, respectively. Its pI, optimum temperature, and pH are 9.5, 45 °C, and 4, respectively. The enzyme is stable below 45 °C and between pH 3 and 5. The enzyme hydrolyzes β-primeveroside into primeverose and an aglycon without further hydrolysis. These enzymic characteristics were found to be quite similar to those of the β-primeverosidase from cv. Yabukita exclusively processed to green tea. As most of the alcoholic tea aroma precursors have been isolated as β-primeverosides, the main route of the aroma formation in oolong tea has been elucidated on a molecular basis. Keywords: β-Primeverosidase; oolong tea; Camellia sinensis; aroma formation; glycosidase; tea aroma