Protein-engineered Bacillus .ALPHA.-Amylases That Have Acquired Both Enhanced Thermostability and Chelator Resistance.

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  • 耐熱性とキレート剤耐性を獲得したBacillus由来のα-アミラーゼ変異体
  • Protein-engineered Bacillus α-Amylases That Have Acquired Both Enhanced Thermostability and Chelator Resistance
  • Protein engineered Bacillus アルファ Amylases That Have Acquired Both Enhanced Thermostability and Chelator Resistance

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Abstract

Thermostability and chelator resistance of the liquefying alkaline α-amylase (AmyK) from alkaliphilic Bacillus sp. strain KSM-1378 were examined by deletion of either Argl81-Glyl82 or Thr 183-G1y184 on a loop in domain B. In the tertiary structure of Bacillus stearothermophilus α-amylase (BSA), Ilel81-Glyl82 (Thr183-G1y184 in AmyK) pushes away a spatially contacting region containing Ca2+-coordinating Asp207 (Asp209 in AmyK). Therefore, the deletion of Ilel81- G1y182 rather than Argl79-G1yl80 was predicted to result in a higher thermostability of BSA. However, our results with AmyK were clearly contrary to this prediction. The resistance to EDTA of both mutant enzymes from AmyK was essentially equal, and the Argl81-Glyl82-deleted mutant was more thermostable than the Thr183-G1y184-deleted one. It strongly implies that the microenvironmental topology around the loop containing these dipeptides in AmyK is different from that in BSA.

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