Purification and characterization of an invertase produced by Aspergillus ochraceus TS

Purification and characterization of an extracellular invertase produced by Aspergillus ochraceus TS are reported. The enzyme was purified (42-fold) from culture filtrate by salt precipitation, ion-exchange and gel filtration. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) of the purified enzyme showed a single band of molecular mass 66 kDa. The molecular mass of the native enzyme was found to be 130 kDa by gel filtration. The purity of the protein was also checked against its antiserum raised in rabbits by two-dimensional immunodiffusion in agarose gel and Western blot that showed a single band. It is a glycoprotein with mannose as its carbohydrate residue. The enzyme showed high affinity for sucrose with a Km of 3.5 mM. The amino acid analysis revealed a high proportion of acidic residues but it had a low content of cysteine, histidine and arginine comparable to other fungal invertases.