Journal of Microbiology

Research Support, Non-U.S. Gov't

Identification of an Extracellular Thermostable Glycosyl Hydrolase Family 13 α-Amylase from Thermotoga neapolitana: Kyoung-Hwa Choi , Sungmin Hwang , Hee-Seob Lee , Jaeho Cha; J. Microbiol. 2011;49(4):628-634. Published online September 2, 2011; DOI: https://doi.org/10.1007/s12275-011-0432-7

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.

Review

REVIEW] The Linkage between Reverse Gyrase and Hyperthermophiles: A Review of Their Invariable Association: Michelle Heine , Sathees B.C. Chandra; J. Microbiol. 2009;47(3):229-234. Published online June 26, 2009; DOI: https://doi.org/10.1007/s12275-009-0019-8

Abstract: With the discovery of reverse gyrase in 1972, from Yellowstone National Park, isolated from Sulfolobus acidocaldarius, it has been speculated as to why reverse gyrase can be found in all hyperthermophiles and just what exactly its role is in hyperthermophilic organisms. Hyperthermophiles have been defined as organisms with an optimal growth temperature of above 85°C. Reverse gyrase is responsible for the introduction of positive supercoils into closed circular DNA. This review of reverse gyrase in hyperthermophilic microorganisms summarizes the last two decades of research performed on hyperthermophiles and reverse gyrase in an effort to provide an up to date synopsis of their invariable association. From the data gathered for this review it is reasonable to hypothesize that reverse gyrase is closely tied to hyperthermophilic life.

Search