title: Cold adaptation of enzymes: structural, kinetic and microcalorimetric characterizations of an aminopeptidase from the Arctic psychrophile Colwellia psychrerythraea and of human leukotriene A(4) hydrolase.
abstract: The relationships between structure, activity, stability and flexibility of a cold-adapted aminopeptidase produced by a psychrophilic marine bacterium have been investigated in comparison with a mesophilic structural and functional human homolog. Differential scanning calorimetry, fluorescence monitoring of thermal- and guanidine hydrochloride-induced unfolding and fluorescence quenching were used to show that the cold-adapted enzyme is characterized by a high activity at low temperatures, a low structural stability versus thermal and chemical denaturants and a greater structural permeability to a quenching agent relative to the mesophilic homolog. These findings support the hypothesis that cold-adapted enzymes maintain their activity at low temperatures as a result of increased global or local structural flexibility, which results in low stability. Analysis of the thermodynamic parameters of irreversible thermal unfolding suggests that entropy-driven factors are responsible for the fast unfolding rate of the cold-adapted aminopeptidase. A reduced number of proline residues, a lower degree of hydrophobic residue burial and a decreased surface accessibility of charged residues may be responsible for this effect. On the other hand, the reduction in enthalpy-driven interactions is the primary determinant of the weak conformational stability.
authors.affiliation: Laboratory of Biochemistry, University of Liège, B-4000 Liège-Sart Tilman, Belgium.
authors.forename: Adrienne L
authors.initials: AL
authors.lastname: Huston
authors.forename: Jesper Z
authors.initials: JZ
authors.lastname: Haeggström
authors.forename: Georges
authors.initials: G
authors.lastname: Feller
mesh_terms: D000222:Adaptation, Physiological; D034241:Alteromonadaceae / Q000201:enzymology*; D000595:Amino Acid Sequence; D000626:Aminopeptidases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism / Q000502:physiology*; D001110:Arctic Regions; D002152:Calorimetry, Differential Scanning; D003080:Cold Temperature; D004851:Epoxide Hydrolases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism / Q000502:physiology*; D005453:Fluorescence; D006801:Humans; D007700:Kinetics; D011487:Protein Conformation; D011489:Protein Denaturation; D017510:Protein Folding; D013329:Structure-Activity Relationship; D013816:Thermodynamics
chemical_list: D004851:Epoxide Hydrolases; D000626:Aminopeptidases; C043134:leukotriene A4 hydrolase