title: Are the catalytic properties of enzymes from piezophilic organisms pressure adapted?
abstract: We report the crystal structure of dihydrofolate reductase (DHFR) from the psychropiezophilic bacterium Moritella profunda, which was isolated from the deep ocean at 2 degrees C and 280 bar. The structure is typical of a chromosomal DHFR and we were unable to identify any obvious structural features that would suggest pressure adaptation. In particular, the core regions of the enzyme are virtually identical to those of the DHFR from the mesophile Escherichia coli. The steady-state rate at pH 9, which is limited by hydride transfer at atmospheric pressure, is roughly constant between 1 and 750 bar, falling at higher pressures. However, the value of K(M) increases with increasing pressure, and as a result k(cat)/K(M) decreases over the entire pressure range studied. Isotope effect studies showed that increasing the pressure causes a change in the rate-limiting step of the reaction. We therefore see no evidence of pressure adaptation in either the structure or the activity of this enzyme.
authors.affiliation: Manchester Interdisciplinary Biocentre and Faculty of Life Sciences, University of Manchester, Manchester M1 7DN, UK.
authors.forename: Sam
authors.initials: S
authors.lastname: Hay
authors.forename: Rhiannon M
authors.initials: RM
authors.lastname: Evans
authors.forename: Colin
authors.initials: C
authors.lastname: Levy
authors.forename: E Joel
authors.initials: EJ
authors.lastname: Loveridge
authors.forename: Xi
authors.initials: X
authors.lastname: Wang
authors.forename: David
authors.initials: D
authors.lastname: Leys
authors.forename: Rudolf K
authors.initials: RK
authors.lastname: Allemann
authors.forename: Nigel S
authors.initials: NS
authors.lastname: Scrutton
mesh_terms: D055162:Biocatalysis; D007700:Kinetics; D008968:Molecular Conformation; D034221:Moritella / Q000201:enzymology; D011312:Pressure; D011994:Recombinant Proteins / Q000378:metabolism; D013762:Tetrahydrofolate Dehydrogenase / Q000378:metabolism*
chemical_list: D011994:Recombinant Proteins; D013762:Tetrahydrofolate Dehydrogenase