Abstract
Extracellular and intracellular amylases have been purified from a thermophilic Bacillus stearothermophilus and further studies have been made with the purified enzyme. The molecular weights for extra- and intracellular α- and β-amylases were found to be 47 000, 58 000, 39 000 and 67 000, respectively. α-Amylase (1,4-α- d-glucan glucanohydrolase, EC 3.2.1.1) and glucoamylase (1,4-α- d-glucan glucohydrolase, EC 3.2.1.3) were glycoproteins, whereas β-amylase (1,4-α- d-glucan maltohydrolase, EC 3.2.1.2) had little or no carbohydrate moiety. Extracellular FI (α-amylase), FIII (glucoamylase), FIV and FV (α-amylase) had carbohydrate moieties of 14.4, 27.0, 11.0 and 12.5%, respectively, whereas intracellular amylases FI (α-amylase), FII (β-amylase) and FIII (α-amylase) contained 15.2, 0.8 and 13.4% carbohydrate, respectively. The amino acid profile of the amylase protein digest showed a total number of 16 amino acids with aspartic acid showing the highest value followed by glutamic acid and leucine plus isoleucine. Compared to other thermostable amylases, proline and histidine contents were low. Both α- and β- amylase had the - SH group at their active site, which was essential for enzyme activity. EDTA and parachloromercuribenzoate exhibited dose dependent non-competitive inhibition of enzyme activity indicating the involvement of a divalent cation and the - SH group for activity .
Published Version
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