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 (t50 of 1.3 min.). Apparent KM for trealose was 0.2 mM. Immunolocalisation studies showed the enzyme tightly packed at the surface of the cells.