title: Enzymes from cold-adapted microorganisms. The class C beta-lactamase from the antarctic psychrophile Psychrobacter immobilis A5.
abstract: A heat-labile beta-lactamase has been purified from culture supernatants of Psychrobacter immobilis A5 grown at 4 degrees C and the corresponding chromosomal ampC gene has been cloned and sequenced. All structural and kinetic properties clearly relate this enzyme to class C beta-lactamases. The kinetic parameters of P. immobilis beta-lactamase for the hydrolysis of some beta-lactam antibiotics are in the same range as the values recorded for the highly specialized cephalosporinases from pathogenic mesophilic bacteria. By contrast, the enzyme displays a low apparent optimum temperature of activity and a reduced thermal stability. Structural factors responsible for the latter property were analysed from the three-dimensional structure built by homology modelling. The deletion of proline residues in loops, the low number of arginine-mediated H-bonds and aromatic-aromatic interactions, the lower global hydrophobicity and the improved solvent interactions through additional surface acidic residues appear to be the main determinants of the enzyme flexibility.
authors.affiliation: Laboratoire de Biochimie, Institut de Chimie B6, Université de Liège, Belgium.
authors.forename: G
authors.initials: G
authors.lastname: Feller
authors.forename: Z
authors.initials: Z
authors.lastname: Zekhnini
authors.forename: J
authors.initials: J
authors.lastname: Lamotte-Brasseur
authors.forename: C
authors.initials: C
authors.lastname: Gerday
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics; D000595:Amino Acid Sequence; D000864:Antarctic Regions; D001483:Base Sequence; D002876:Chromosomes, Bacterial; D003080:Cold Temperature; D004795:Enzyme Stability; D005798:Genes, Bacterial; D006088:Gram-Negative Aerobic Bacteria / Q000201:enzymology* / Q000235:genetics / Q000502:physiology; D006358:Hot Temperature; D008969:Molecular Sequence Data; D001618:beta-Lactamases / Q000096:biosynthesis / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*
chemical_list: D001618:beta-Lactamases