title: Exploring the thermal stability and activity of α-chymotrypsin in the presence of spermine.
abstract: Polyamines such as spermine can have interaction with protein. The aim of the present study was to investigate how spermine could influence the structure, thermal stability, and the activity of α-chymotrypsin. Kinetics, thermodynamics, molecular dynamics (MD), and docking simulations studies were conducted to investigate the effect of spermine on the activity and structure of α-Chymotrypsin (α-Chy) in 50 mM Tris-HCl buffer, with the pH 8, using different spectroscopic techniques as well as molecular docking and MD simulations. The stability and activity of α-Chy were increased in the presence of spermine. The results of the kinetic study showed that the activity of spermine was increased. Enzyme activation was accompanied by changes on the α-Chy conformation. Fluorescence intensity changes showed dynamic quenching during spermine binding. The fluorescence quenching of the α-Chy suggested the more polar location of Trp residues. Near-UV and Far-UV circular dichroism studies also demonstrated the transfer of Trp, Phe, and Tyr residues to a more flexible environment. The increase in the absorption of α-Chy in the presence of spermine was as a result of the formation of spermine-α-Chy complex. Molecular docking results revealed the presence of one binding site with a negative value for the Gibbs free energy of the binding of spermine to α-Chy. Docking study also revealed that van der Waals interactions and hydrogen bonds played a major role in stabilizing the complex.
authors.affiliation: a Faculty of Science, Department of Biology , University of Shahrekord , Shahrekord , P. O. Box. 115 , Iran.
authors.forename: Sadegh
authors.initials: S
authors.lastname: Farhadian
authors.affiliation: a Faculty of Science, Department of Biology , University of Shahrekord , Shahrekord , P. O. Box. 115 , Iran.
authors.forename: Behzad
authors.initials: B
authors.lastname: Shareghi
authors.affiliation: b Institute of Biochemistry and Biophysics, University of Tehran , Tehran , Iran.|c Center of Excellence in Biothermodynamics, University of Tehran , Tehran , Iran.
authors.forename: Ali A
authors.initials: AA
authors.lastname: Saboury
mesh_terms: D002918:Chymotrypsin / Q000737:chemistry* / Q000378:metabolism; D004795:Enzyme Stability / Q000187:drug effects; D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D008958:Models, Molecular; D008968:Molecular Conformation; D062105:Molecular Docking Simulation; D056004:Molecular Dynamics Simulation; D013057:Spectrum Analysis; D013096:Spermine / Q000737:chemistry* / Q000494:pharmacology; D013329:Structure-Activity Relationship; D013816:Thermodynamics
chemical_list: D013096:Spermine; D002918:Chymotrypsin; C117608:alpha-chymotrypsin
keywords: docking simulations; molecular dynamics; spectroscopic techniques; thermal stability; α-chymotrypsin