title: Structural stability and functional analysis of L-asparaginase from Pyrococcus furiosus.
abstract: We report studies on an L-asparaginase from Pyrococcus furiosus, cloned and expressed in Escherichia coli and purified to homogeneity. Protein stability and enzyme kinetic parameters were determined. The enzyme was found to be thermostable, natively dimeric, and glutaminase-free, with optimum activity at pH 9.0. It showed a K(m) of 12 mM and a substrate inhibition profile above 20 mM L-asparagine. Urea could not induce unfolding and enzyme inactivation; however, with guanidine hydrochloride (GdnCl) a two-state unfolding pattern was observed. Reduced activity and an altered near-UV-CD signal for protein at low GdnCl concentration (1 M) suggested tertiary structural changes at the enzyme active site. A homology three-dimensional model was developed and the structural information was combined with activity and stability data to give functional clues about the asparaginase.
authors.affiliation: Department of Biochemical Engineering and Biotechnology, Indian Institute of Technology Delhi, Hauz Khas, New Delhi, India.
authors.forename: S
authors.initials: S
authors.lastname: Bansal
authors.forename: D
authors.initials: D
authors.lastname: Gnaneswari
authors.forename: P
authors.initials: P
authors.lastname: Mishra
authors.forename: B
authors.initials: B
authors.lastname: Kundu
mesh_terms: D001215:Asparaginase / Q000378:metabolism*; D001483:Base Sequence; D017931:DNA Primers; D004795:Enzyme Stability; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D020027:Pyrococcus furiosus / Q000201:enzymology*
chemical_list: D017931:DNA Primers; D001215:Asparaginase