Open AccessDifferences in malate dehydrogenases from the obligately piezophilic deep‐sea bacterium Moritella sp. strain 2D2 and the psychrophilic bacterium Moritella sp. strain 5710 1
Author(s) -
Saito Rie,
Nakayama Akihiko
Publication year - 2004
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1016/j.femsle.2004.02.004
Subject(s) - psychrophile , malate dehydrogenase , strain (injury) , biology , bacteria , biochemistry , genetics , enzyme , anatomy
The gene encoding malate dehydrogenase (MDH) of the obligately piezophilic deep‐sea bacterium Moritella sp. strain 2D2 was cloned and sequenced. There were two positions [close to the active site (Ala‐180) and in the subunit interaction site (His‐229)] with 2D2‐specific substitutions. The MDH genes of strain 2D2 and a psychrophilic bacterium Moritella sp. strain 5710 exhibiting the highest sequence similarity were overexpressed in Escherichia coli . The 2D2 MDH was more heat‐stable than the 5710 MDH. The apparent K m value at 62.1 MPa for NADH of the 2D2 MDH was higher than that of the 5710 MDH. The 2D2 MDH in which a His–Gln substitution was introduced at position 229 decreased the thermal stability and K m value at 62.1 MPa. The 5710 MDH that was substituted Gln‐229 with His increased the thermal stability and K m value at 62.1 MPa. These results indicate that the His residue at position 229 of the 2D2 MDH may play a role in the thermal stability and the MDH function at high pressure.