Purification and characterization of an alpha-L-rhamnosidase from Pichia angusta X349.

An intracellular alpha-L-rhamnosidase from Pichia angusta X349 was purified to homogeneity through four chromatographic steps. The alpha-L-rhamnosidase appeared to be a monomeric protein with a molecular mass of 90 kDa. The enzyme had an isoelectric point at 4.9, and was optimally active at pH 6.0 and at around 40 degrees C. The Ki for L-rhamnose inhibition was 25 mM. The enzyme was inhibited by Cu2+, Hg2+, and p-chloromercuribenzoate. The alpha-L-rhamnosidase was highly specific for alpha-L-rhamnopyranoside and liberated rhamnose from naringin, rutin, hesperidin, and 3-quercitrin. The alpha-L-rhamnosidase was active at the ethanol concentrations of wine. It efficiently released monoterpenols, such as linalool and geraniol, from an aroma precursor extracted from Muscat grape juice.