Improved Thermostability of aBacillusα-Amylase by Deletion of an Arginine-Glycine Residue Is Caused by Enhanced Calcium Binding

Mutant Luciferase Enzymes from Fireflies with Increased Resistance to Benzalkonium Chloride

“…Therefore, the increase of thermostability by amino acid replacement at position 217 has been considered to be due to an improvement in the density and rigidity of core packing, 9) resulting in more resistance to BAC, not only to heat denaturation. The thermostable mutants of kanamycin nucleotidyltransferase 29) and a-amylase 30) also show increased resistance to other types of protein denaturation agents, including surfactants. Unlike position 217, position 490 (Glu) in LlL, corresponding to position 488 in PpL, is located on the surface of the luciferase enzyme and is part of a loop in the compact C-terminal domain on a side of the large cleft separating the C-terminal and N-terminal domains.…”

Purification and Characterization of a Liquefying α-Amylase from Alkalophilic ThermophilicBacillussp. AAH-31

“…The resulting mutant enzyme was stable at 70 C at pH 8.5 for 10 min in the presence of 0.1 mM CaCl 2 , but its thermostability decreased significantly in the absence of the calcium ion. 13,14) Recently, alkalitolerantamylases, which were highly stable at 60 C in the absence of the calcium ion, were found in Anoxybacillus species, 15) but the enzymes predominantly produced maltose from starch even at the initial stage of the reaction, indicating that they are saccharifying enzymes, not suitable for use in detergents. In this study, we screened a thermostable alkaline liquefying -amylase with high resistance to chelating regents from soil bacteria, and successfully obtained an enzyme with the required properties from Bacillus sp.…”

Molecular Modeling and Implications of a Bacillus .ALPHA.-Amylase that Acquires Enhanced Thermostability and Chelator Resistance by Deletion of an Arginine-glycine Residue

“…8) also suggested that the loop containing the Arg Gly residue is enlarged in BAA by two more amino acid residues than in BLA and that this could cause increased mobility of this region and decreased thermostability of the whole protein. However, because AmyK acquires not only thermostability but also resistance to EDTA and EGTA significantly by the Arg181 Gly182 deletion (dRG) mutation, 9) the above hypotheses cannot explain the chelator resistance of the mutation.…”