Enhancement of the thermostability of the maltogenic amylase MAUS149 by Gly312Ala and Lys436Arg substitutions.
ABSTRACT Based on sequence alignments and homology modeling, Gly 312 and Lys 436 of the maltogenic amylase from Bacillus sp. US149 (MAUS149) were selected as targets for site-directed mutagenesis to improve the thermostability of the enzyme. Variants of MAUS149 with amino acid substitutions G312A, K436R and G312A-K436R had substrate specificities, kinetic parameters and pH optima similar to those of the wild-type enzyme; however, the enzymes with substitutions K436R and G312A-K436R, had an optimal temperature of 45 °C instead of the 40 °C for the wild-type enzyme. The half-life time at 55 °C increased from 15 to 25 min for the double mutant. Molecular modeling suggests that the increase in thermostability was due to new hydrophobic interactions and the formation of a salt bridge and hydrogen bond in the G312A and K436R variants, respectively. The double mutant could be a potential candidate for application in the bread industry.
Article: From protein engineering to immobilization: promising strategies for the upgrade of industrial enzymes.[show abstract] [hide abstract]
ABSTRACT: Enzymes found in nature have been exploited in industry due to their inherent catalytic properties in complex chemical processes under mild experimental and environmental conditions. The desired industrial goal is often difficult to achieve using the native form of the enzyme. Recent developments in protein engineering have revolutionized the development of commercially available enzymes into better industrial catalysts. Protein engineering aims at modifying the sequence of a protein, and hence its structure, to create enzymes with improved functional properties such as stability, specific activity, inhibition by reaction products, and selectivity towards non-natural substrates. Soluble enzymes are often immobilized onto solid insoluble supports to be reused in continuous processes and to facilitate the economical recovery of the enzyme after the reaction without any significant loss to its biochemical properties. Immobilization confers considerable stability towards temperature variations and organic solvents. Multipoint and multisubunit covalent attachments of enzymes on appropriately functionalized supports via linkers provide rigidity to the immobilized enzyme structure, ultimately resulting in improved enzyme stability. Protein engineering and immobilization techniques are sequential and compatible approaches for the improvement of enzyme properties. The present review highlights and summarizes various studies that have aimed to improve the biochemical properties of industrially significant enzymes.International Journal of Molecular Sciences 01/2013; 14(1):1232-77. · 2.60 Impact Factor