title: Mercuric ion stabilizes levansucrase secreted by Acetobacter nitrogenifigens strain RG1(T).
abstract: The purification and characterization of an extracellular levansucrase enzyme produced by novel nitrogen-fixer Acetobacter nitrogenifigens strain RG1(T) is described. Culture conditions were optimized for maximum levansucrase production. Levansucrase purified to homogeneity by tenfold purification has a molecular weight of 65 kDa, contained four cysteine residues, polymerized raffinose and was stable for 21 days at pH 6.0 when stored at 4 °C or -20 °C but was vulnerable to DTT and β-mercaptoethanol. Interestingly, this enzyme showed enhanced hydrolytic and polymerization activity in the presence of mercuric ion which, to our knowledge, is the first report for any levansucrase enzyme characterized so far. Evidences obtained from Native PAGE, tryptophan fluorescence study and activity measurements at different temperatures and in the presence of thiol modifying agents, show that mercuric ion stabilizes the enzyme. Levan, synthesized by the enzyme, has a molecular weight of 7,080 kDa and was shown to be a homopolymer of fructose.
authors.affiliation: Department of Life Science and Biotechnology, Jadavpur University, 188 Raja S.C. Mullick Road, Kolkata, 700032, India.
authors.forename: Arundhati
authors.initials: A
authors.lastname: Paul
authors.forename: Neeloy
authors.initials: N
authors.lastname: Samaddar
authors.forename: Debasree
authors.initials: D
authors.lastname: Dutta
authors.forename: Abhishek
authors.initials: A
authors.lastname: Bagchi
authors.forename: Somnath
authors.initials: S
authors.lastname: Chakravorty
authors.forename: Writachit
authors.initials: W
authors.lastname: Chakraborty
authors.forename: Ratan
authors.initials: R
authors.lastname: Gachhui
mesh_terms: D000091:Acetobacter / Q000737:chemistry / Q000201:enzymology* / Q000378:metabolism; D003545:Cysteine / Q000032:analysis; D005630:Fructans / Q000378:metabolism; D006602:Hexosyltransferases / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism*; D008628:Mercury / Q000378:metabolism*; D055550:Protein Stability
chemical_list: D005630:Fructans; C072599:levan; D006602:Hexosyltransferases; C021513:levansucrase; D008628:Mercury; D003545:Cysteine