α-Amylase activity from the halophilic archaeon Haloferax mediterranei

Abstract

The halophilic archaeon Haloferax mediterranei is able to grow in a minimal medium containing ammonium acetate as a carbon and nitrogen source. When this medium is enriched with starch, alpha-amylase activity is excreted to the medium in low concentration. Here we report methods to concentrate and purify the enzyme. The relative molecular mass of the enzyme, determined by gel filtration, is 50 +/- 4 kDa, and on SDS-PAGE analysis a single band appeared at 58 kDa. These results indicated that the halophilic alpha-amylase is a monomeric enzyme. The enzyme showed a salt requirement for both stability and activity, being stable from 2 to 4 M NaCl, with maximal activity at 3 M NaCl. The enzyme displayed maximal activity at pHs from 7 to 8, and its optimal temperature was in a range from 50 degrees C to 60 degrees C. The results also implicated several prototropic groups in the catalytic reaction.

Gene Analysis, Expression, and Characterization of an Intracellular α-Amylase from the Extremely Halophilic Archaeon <i>Haloarcula japonica</i>

“…Many -amylases have been identified in various organisms, but those from extremely halophilic archaea are less well-known. To date, a maltotrioseforming -amylase from Natronococcus amylolyticus, 30) an -amylase from Haloferax mediterranei, 31) and an -amylase from Haloarcula hispanica 32) have been reported. These four -amylases, including MalA, are equally halophilic.…”

Isolation, characterization and identification of amylase producing halothermophilic isolates from Howz Soltan Lake, Iran

“…However, enzyme production were stable at 60°C, but the enzyme stability was better than that of other researcher findings (Tan et al, 2008;Prakash et al, 2009). Therefore, according to the findings it should be noted that the amylase producing halothermophilic strains might be called halophilic because the halophilic enzymes are usually inactive when the NaCl or KCl concentration is less than 2 M (Mader et al, 2000) as Pomares et al (2003) showed that the optimum salt concentration for amylase production of Haloferax mediterranei was 3 M NaCl. Therefore, this halophilic stability and adaptation of halothermophilic strains with capability to produce amylase (higher than the other halophilic strains than that of other researcher isolates) suggested that, these strains could be a good choice for some biotechnological application.…”

Biocompounds from Haloarchaea and Their Uses in Biotechnology

“…Some halophilic amylases from Archaea have been characterized [51][52][53][54][55]. Most of them retain their activity at high temperatures.…”

“…Most of them retain their activity at high temperatures. For example, the haloarchaeon H. mediterranei secretes an α-amylase showing optimum temperature between 50 and 60°C, but it retains 65% of the maximum activity at 80°C [55]. H. mediterranei also has a monomeric extracellular cyclodextrin glycosyltransferase working optimally at 55°C and 1.5 M NaCl, but it is active even at low salt concentrations as 0.5 M NaCl (retaining 65% of its activity) [56].…”