title: [Purification and properties of recombinant extremely thermostable and acid-stable amylase].
abstract: Extremely thermostable and acid-stable a-amylase produced by Pichia pastoris GS115/pPIC9K-Amy-228 was purified to electrophoretic homogeneity by the steps of ultrafiltration and PAGE. Purification of about 11.7 fold was achieved with an overall yield of 29.8%. Its molecular weight was estimated to be about 55kD by SDS-PAGE. The isoelectric point was 5.0 (room temperature). Michaelis constant of the enzyme for soluble starch was 1.12g/L. The carbohydrate content was 15.4% by the phenol-sulfuric acid method. The optimum temperature and pH of the enzyme activity were 95 degrees C and 4.5 respectively. The enzyme activity was stable under room temperature in the pH rang of 4.0 - 7.0 for 48 hours. About 60% of the initial enzyme activity was measured after 1h of incubation at 110 degrees C. The activity was strongly inhibited by Fe2+, Cr2+ and Cu2+, While Ca2+ had no effect on it. DTT and EDTA had no effect on the activity.
authors.affiliation: Institute of Microbiology, Beijing 100080, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Li
authors.forename: Jian-Qiang
authors.initials: JQ
authors.lastname: Guo
authors.forename: Li-Li
authors.initials: LL
authors.lastname: Yue
authors.forename: Yun-Min
authors.initials: YM
authors.lastname: Li
authors.forename: Qing-Hu
authors.initials: QH
authors.lastname: Jiao
mesh_terms: D000681:Amylases / Q000302:isolation & purification* / Q000378:metabolism; D004795:Enzyme Stability; D006863:Hydrogen-Ion Concentration; D008970:Molecular Weight; D010843:Pichia / Q000201:enzymology / Q000235:genetics; D011994:Recombinant Proteins / Q000302:isolation & purification; D013696:Temperature
chemical_list: D011994:Recombinant Proteins; D000681:Amylases