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

• Published in: Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics
• Main Authors: Huston, A. L., Haeggstrom, J. Z., Feller, Georges
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2008
• Subjects: *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; Life sciences; Biochemistry; biophysics & molecular biology; Sciences du vivant; Biochimie; biophysique & biologie moléculaire; Arctic
• Online Access: https://orbi.uliege.be/handle/2268/16609; https://doi.org/10.1016/j.bbapap.2008.06.002

peer reviewed 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.