Characterisation of an acid trehalase produced by the thermotolerant fungus Rhizopus microsporus var. rhizopodiformis : Biochemical properties and immunochemical localisation

An acid trehalase from Rhizopus microsporus var. rhizopodiformis was purified to apparent homogeneity. The molecular weight by SDS–PAGE (60 kDa) or Sephacryl S‐200 filtration (105 kDa) suggested a homodimer. The carbohydrate content was 72%. Endoglycosidase H digestion resulted in one sharp band of 51.5 kDa in SDS–PAGE. pH and temperature optima were 4.5 and 45 °C, respectively. The isoelectric point was 6.69 and activation energy was 1.14 kcal mol −1 . The enzyme was stable for 1 h at 50 °C and decayed at 60 °C ( t 50 of 1.3 min.). Apparent K M for trealose was 0.2 mM. Immunolocalisation studies showed the enzyme tightly packed at the surface of the cells.