Reference : Cold adaptation of enzymes: structural, kinetic and microcalorimetric characterizations ...
Scientific journals : Article
Life sciences : Biochemistry, biophysics & molecular biology
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
[en] *Adaptation, Physiological ; Alteromonadaceae/*enzymology ; Amino Acid Sequence ; Aminopeptidases/chemistry/isolation & purification/metabolism/*physiology ; Arctic Regions ; Calorimetry, Differential Scanning ; *Cold Temperature ; Epoxide Hydrolases/chemistry/isolation & ; purification/metabolism/*physiology ; Fluorescence ; Humans ; Kinetics ; Protein Conformation ; Protein Denaturation ; Protein Folding ; Structure-Activity Relationship ; Thermodynamics
[en] 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.