Identification of amino acid residues responsible for increased thermostability of feruloyl esterase A from Aspergillus niger using the PoPMuSiC algorithm.
Feruloyl esterases are key enzymes involved in the complete hydrolysis of hemicellulose. In order to improve the thermostability of feruloyl esterase A (FaeA) from Aspergillus niger CIB 423.1, the PoPMuSiC algorithm was applied to predict the folding free energy change (ΔΔG) of amino acid substitutions. Four amino acid substitutions (S92A, D93G, D174A and S187F) were introduced into the enzyme by site-directed mutagenesis and the enzymes were produced in Pichia pastoris KM71. No obvious changes in thermal stability resulted from substitutions S92A and D174A, but, compared to the wild-type enzyme which has a half-life of inactivation of 8 min, the half-lives of enzymes with a D93G or S187F substitution increased to 9.4 and 60.5 min, respectively. The double mutant D93G/S187F displayed a synergistic effect with a t1/2 value of 77.0 min. It also displayed over 10-fold increase in catalytic turnover frequency. The result will benefit further investigation of the thermostability of feruloyl esterase A.
Zhang
Shuai-Bing
SB
Chengdu Institute of Biology, Chinese Academy of Sciences, P.O. Box 416, Chengdu 610041, PR China.
Wu
Zhong-Liu
ZL
D000465:Algorithms; D019943:Amino Acid Substitution / Q000235:genetics*; D000596:Amino Acids / Q000235:genetics*; D001234:Aspergillus niger / Q000201:enzymology* / Q000235:genetics*; D002265:Carboxylic Ester Hydrolases / Q000235:genetics* / Q000378:metabolism; D004795:Enzyme Stability; D007700:Kinetics; D050505:Mutant Proteins / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D010843:Pichia / Q000378:metabolism; D013696:Temperature
D000596:Amino Acids; D050505:Mutant Proteins; D002265:Carboxylic Ester Hydrolases; C070196:feruloyl esterase