Purification and characterization of a liquefying α-amylase from alkalophilic thermophilic Bacillus sp. AAH-31.
α-Amylase (EC 3.2.1.1) hydrolyzes an internal α-1,4-glucosidic linkage of starch and related glucans. Alkalophilic liquefying enzymes from Bacillus species are utilized as additives in dishwashing and laundry detergents. In this study, we found that Bacillus sp. AAH-31, isolated from soil, produced an alkalophilic liquefying α-amylase with high thermostability. Extracellular α-amylase from Bacillus sp. AAH-31 (AmyL) was purified in seven steps. The purified enzyme showed a single band of 91 kDa on SDS-PAGE. Its specific activity of hydrolysis of 0.5% soluble starch was 16.7 U/mg. Its optimum pH and temperature were 8.5 and 70 °C respectively. It was stable in a pH range of 6.4-10.3 and below 60 °C. The calcium ion did not affect its thermostability, unlike typical α-amylases. It showed 84.9% of residual activity after incubation in the presence of 0.1% w/v of EDTA at 60 °C for 1 h. Other chelating reagents (nitrilotriacetic acid and tripolyphosphate) did not affect the activity at all. AmyL was fully stable in 1% w/v of Tween 20, Tween 80, and Triton X-100, and 0.1% w/v of SDS and commercial detergents. It showed higher activity towards amylose than towards amylopectin or glycogen. Its hydrolytic activity towards γ-cyclodextin was as high as towards short-chain amylose. Maltotriose was its minimum substrate, and maltose and maltotriose accumulated in the hydrolysis of maltooligosaccharides longer than maltotriose and soluble starch.
Research Faculty of Agriculture, Hokkaido University, Sapporo, Japan.
Dae Hoon
DH
Kim
Naoki
N
Morimoto
Wataru
W
Saburi
Atsushi
A
Mukai
Koji
K
Imoto
Toshihiko
T
Takehana
Seiji
S
Koike
Haruhide
H
Mori
Hirokazu
H
Matsui
D000688:Amylose / Q000378:metabolism; D001407:Bacillus / Q000737:chemistry / Q000201:enzymology*; D001426:Bacterial Proteins / Q000302:isolation & purification* / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D004492:Edetic Acid / Q000737:chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D004795:Enzyme Stability; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008970:Molecular Weight; D017830:Octoxynol / Q000737:chemistry; D011136:Polysorbates / Q000737:chemistry; D012967:Sodium Dodecyl Sulfate / Q000737:chemistry; D012988:Soil Microbiology; D013213:Starch / Q000378:metabolism; D013379:Substrate Specificity; D000516:alpha-Amylases / Q000302:isolation & purification* / Q000378:metabolism; D047408:gamma-Cyclodextrins / Q000378:metabolism
D001426:Bacterial Proteins; D011136:Polysorbates; D047408:gamma-Cyclodextrins; D012967:Sodium Dodecyl Sulfate; D017830:Octoxynol; D013213:Starch; D000688:Amylose; D004492:Edetic Acid; D000516:alpha-Amylases; C023792:gamma-cyclodextrin; D002118:Calcium