| Title |
Identification of an Extracellular Thermostable Glycosyl Hydrolase Family 13 α-Amylase from Thermotoga neapolitana |
| Author |
Kyoung-Hwa Choi1, Sungmin Hwang1, Hee-Seob Lee2, and Jaeho Cha1* |
| Address |
1Department of Microbiology, College of Natural Sciences, Pusan National University, Busan 609-735, Republic of Korea, 2Department of Food and Nutrition, Pusan National University, Busan 609-735, Republic of Korea |
| Bibliography |
Journal of Microbiology, 49(4),628-634, 2011,
|
| DOI |
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| Key Words |
GH 13 α-amylase, hyperthermophiles, thermostability, Thermotoga neapolitana |
| Abstract |
We cloned the gene for an extracellular α-amylase, AmyE, from the hyperthermophilic bacterium Thermotoga
neapolitana and expressed it in Escherichia coli. The molecular mass of the enzyme was 92 kDa as a monomer.
Maximum activity was observed at pH 6.5 and temperature 75°C and the enzyme was highly thermostable.
AmyE hydrolyzed the typical substrates for α-amylase, including soluble starch, amylopectin, and maltooligosaccharides.
The hydrolytic pattern of AmyE was similar to that of a typical α-amylase; however, unlike
most of the calcium (Ca2+)-dependent α-amylases, the activity of AmyE was unaffected by Ca2+. The specific
activities of AmyE towards various substrates indicated that the enzyme preferred maltooligosaccharides
which have more than four glucose residues. AmyE could not hydrolyze maltose and maltotriose. When
maltoheptaose was incubated with AmyE at the various time courses, the products consisting of maltose
through maltopentaose was evenly formed indicating that the enzyme acts in an endo-fashion. The specific
activity of AmyE (7.4 U/mg at 75°C, pH 6.5, with starch as the substrate) was extremely lower than that
of other extracellular α-amylases, which indicates that AmyE may cooperate with other highly active extracellular
α-amylases for the breakdown of the starch or α-glucans into maltose and maltotriose before transport
into the cell in the members of Thermotoga sp. |
