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Glucosidase, Beta - Manual
Source:
Almonds
CAS:
9001-22-3
EC:
3.2.1.21
β-Glucosidases catalyze the hydrolysis of glucosides:
Emulsin originally was the term applied to the extract of sweet almonds. It remains as the historical prototype of β-glucosidase. Many other sources of the enzyme have been described. Emulsin also shows significant D-galactosidase activity and there is some question as to whether or not it is one enzyme with two activities, because non-parallel response to inhibitors points to two separate enzymes. D-mannosidase has also been reported in almond emulsin (Schwartz et al. 1970). The enzyme has been reviewed by Veibel (1950), Larner (1960), and Nisizawa and Hashimoto (1970).
Characteristics of β-Glucosidase from Almond:
Specificity
β-glucosides and β-galactosides are reportedly substrates for the enzyme (Kelemen and Whelan 1966). β-D-fucosides are also attacked (Conchie et al. 1967). This is questioned by Schwartz et al. (1970) who offer data supporting the existence of separate enzymes.
Characteristics of Glucosidase, Beta
Molecular Weight
2 active components, 117,000 and 66,500 (Helferich and Kleinschmidt 1965).
Optimal pH
Butyryl glycoside in acetate, pH 4.4 (Veible 1950), p-nitrophenyl glycoside 5.2 - 6.0 (Schwartz et al. 1970).
Inhibitors
HgCl2, other heavy metal ions, sulfhydryl-binding compounds and polyols.
Stability
The enzyme is stable for 1 - 2 years at 2-8°C.
There has been interest in the mammalian form of the enzyme, particularly in relation to Gaucher's disease. Losman (1974) reported that an iso-enzyme of β-glucosidase is lacking in the lymphocytes of homozygotes and a significant decrease is found in heterozygotes. Spleen and liver enzyme activity was lowered in Gaucher's patients when assayed with the synthetic substrate, 4-methylumbelliferal β-D-glycoside.
Constants
Km (M) Glu-I 0.072 (Schwartz et al 1970.)
Glu-II 0.080 (Schwartz et al. 1970)