Purification and characterization of extracellular alpha-amylase from Aspergillus fumigatus

✍ Scribed by Véronique Planchot; Paul Colonna

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 699 KB
• Volume: 272
• Category: Article
• ISSN: 0008-6215
• DOI: 10.1016/0008-6215(95)00035-r

✦ Synopsis

Extracellular alpha-amylase [(1 ~4)-a-D-glucan glucanohydrolase, EC 3.2.1.1] from Aspergillus fumigatus (Aspergillus sp. K-27) was purified to homogeneity by anion-exchange (DEAE-cellulose) and affinity (a-cyclodextrin-Sepharose) chromatography. The purified enzyme, a glycoprotein with 15% carbohydrate content, showed an isoelectric point of 3.7, a molecular weight of 65,000 (as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis), and an amino acid composition with a high number of neutral hydrophobic residues. Alpha-amylase activity on ot-o-glucans in solution was optimal at pH 5.5, and the enzyme was stable at 40°C. It hydrolyzed amylose and amylopectin, with respective K m of 0.42 and 7.7 mg mL-1 and kcat/K m of 3.4 and 2.5 mL mg -1 rain-1. The major end-products of maltohexaose, degradation were glucose and maltose. Maltotriose, maltotetraose, and maltopentaose were formed as intermediate products with an a-anomeric configuration. Despite its ability to slowly degrade some a-(1 ~ 6) linkages, this purified enzyme should be classified as an alpha-amylase.