ABSTRACT
Microbial xylanolytic enzymes have a promising biotechnological potential, and are extensively applied in industries. In this study, induction of xylanolytic activity was examined in Aspergillus phoenicis. Xylanase activity induced by xylan, xylose or beta-methylxyloside was predominantly extracellular (93-97%). Addition of 1% glucose to media supplemented with xylan or xylose repressed xylanase production. Glucose repression was alleviated by addition of cAMP or dibutyryl-cAMP. These physiological observations were supported by a Northern analysis using part of the xylanase gene ApXLN as a probe. Gene transcription was shown to be induced by xylan, xylose, and beta-methylxyloside, and was repressed by the addition of 1% glucose. Glucose repression was partially relieved by addition of cAMP or dibutyryl cAMP.
Subject(s)
Aspergillus/enzymology , Endo-1,4-beta Xylanases/genetics , Endo-1,4-beta Xylanases/metabolism , Gene Expression Regulation, Enzymologic , Gene Expression Regulation, Fungal , Amino Acid Sequence , Aspergillus/classification , Aspergillus/genetics , Cyclic AMP/metabolism , Endo-1,4-beta Xylanases/chemistry , Fungal Proteins/chemistry , Fungal Proteins/genetics , Fungal Proteins/metabolism , Molecular Sequence Data , Sequence Alignment , Transcription, GeneticABSTRACT
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 degrees 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 degrees C and decayed at 60 degrees C (t50 of 1.3 min.). Apparent KM for trealose was 0.2mM. Immunolocalisation studies showed the enzyme tightly packed at the surface of the cells.
