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Two enzymes that hydrolysed lactose were purified essentially to homogeneity from cell extracts of the oleaginous yeast Trichosporon cutaneum. One enzyme of M r 120000 had properties typical of a β-galactosidase (EC 3.2.1.23). It hydrolysed lactose, lactulose and nitrophenyl-β-d-galactosides. The enzyme required K+ or Rb+ for activity, and other monovalent cations tested were not effective. Enzyme activity was abolished by EDTA and stimulated by Mg2+, Mn2+ and Ca2+. The β-galactosidase was induced by lactose, galactose, lactulose and lactobionic acid. The other enzyme, a β-glycosidase (EC 3.2.1.21) of M r 52000 showed no ionic requirements and it hydrolysed lactose, nitrophenyl-β-d-galactosides, 4-nitrophenyl-β-d-glucoside, cellobiose, laminaribiose, laminaritriose and sophorose, but not gentiobiose, 4-nitrophenyl-β-d-mannoside or sucrose. This enzyme was induced by lactose, galactose and lactulose, and also by cellobiose.
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