title: Deleting the Ig-Like Domain of Alicyclobacillus acidocaldarius Endoglucanase Cel9A Causes a Simultaneous Increase in the Activity and Stability.
abstract: Endoglucanase Cel9A from Alicyclobacillus acidocaldarius (AaCel9A) is a monomeric enzyme with 537 residues. This enzyme has an Ig-like domain in the N-terminus of the catalytic domain. In this study, the role of the Ig-like domain on the activity, stability, and structural rigidity of AaCel9A and the effect of calcium on enzyme activity and stability were examined by comparing a truncated enzyme with deletion of the Ig-like domain (AaCel9AΔN) to the wild-type enzyme. Our results showed that the deletion of the Ig-like domain increased the catalytic efficiency of the truncated enzyme up to threefold without any significant changes in the K m of the enzyme. Furthermore, pH and temperature optimum for activity were shifted from 6.5 to 7.5 and from 65 to 60 °C, respectively, by deletion of the Ig-like domain. The thermal stability and fluorescence quenching results indicated that the stability and rigidity of the truncated enzyme have been more than that of the wild-type enzyme. Calcium similarly increased the catalytic efficiency of the enzymes (up to 40 %) and remarkably raised the stability of the AaCel9A compared to the AaCel9AΔN. This shows that Ig-like domain has a role in the increase of the enzyme stability by calcium in the wild-type enzyme.
authors.affiliation: Department of Cellular and Molecular Biology, Faculty of Science, Azarbaijan Shahid Madani University, Tabriz, Iran.
authors.forename: Fereshteh S
authors.initials: FS
authors.lastname: Younesi
authors.affiliation: Department of Cellular and Molecular Biology, Faculty of Science, Azarbaijan Shahid Madani University, Tabriz, Iran. mpazhang@yahoo.com.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Pazhang
authors.affiliation: Department of Cellular and Molecular Biology, Faculty of Science, Azarbaijan Shahid Madani University, Tabriz, Iran.
authors.forename: Saeed
authors.initials: S
authors.lastname: Najavand
authors.affiliation: Department of Cellular and Molecular Biology, Faculty of Science, Azarbaijan Shahid Madani University, Tabriz, Iran.
authors.forename: Parastou
authors.initials: P
authors.lastname: Rahimizadeh
authors.affiliation: Department of Cellular and Molecular Biology, Faculty of Science, Azarbaijan Shahid Madani University, Tabriz, Iran.
authors.forename: Mohsen
authors.initials: M
authors.lastname: Akbarian
authors.affiliation: Department of Nanobiotechnology, Faculty of Biological Science, Tarbiat Modares University, Tehran, Iran.
authors.forename: Mehdi
authors.initials: M
authors.lastname: Mohammadian
authors.affiliation: Department of Biochemistry, Faculty of Biological Science, Tarbiat Modares University, Tehran, Iran.
authors.forename: Khosro
authors.initials: K
authors.lastname: Khajeh
mesh_terms: D056450:Alicyclobacillus / Q000737:chemistry / Q000201:enzymology*; D000595:Amino Acid Sequence / Q000235:genetics; D002118:Calcium / Q000378:metabolism; D020134:Catalytic Domain; D002480:Cellulase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D004795:Enzyme Stability; D017384:Sequence Deletion; D013379:Substrate Specificity
chemical_list: C074775:CelA endoglucanase; D002480:Cellulase; D002118:Calcium
keywords: Calcium; Catalytic efficiency; Endoglucanase Cel9A; Enzyme rigidity; Ig-like domain; Thermal stability