title: Differences in malate dehydrogenases from the obligately piezophilic deep-sea bacterium Moritella sp. strain 2D2 and the psychrophilic bacterium Moritella sp. strain 5710.
abstract: 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 Km 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 Km value at 62.1 MPa. The 5710 MDH that was substituted Gln-229 with His increased the thermal stability and Km 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.
authors.affiliation: Department of Fisheries, Faculty of Agriculture, Kinki University, 204-3327 Nakamachi, Nara City 631-8505, Japan.
authors.forename: Rie
authors.initials: R
authors.lastname: Saito
authors.forename: Akihiko
authors.initials: A
authors.lastname: Nakayama
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D003001:Cloning, Molecular; D003080:Cold Temperature; D004269:DNA, Bacterial / Q000737:chemistry / Q000302:isolation & purification; D004275:DNA, Ribosomal / Q000737:chemistry / Q000302:isolation & purification; D004795:Enzyme Stability; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D005798:Genes, Bacterial; D020459:Genes, rRNA; D006874:Hydrostatic Pressure; D007700:Kinetics; D008291:Malate Dehydrogenase / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D008969:Molecular Sequence Data; D034221:Moritella / Q000201:enzymology* / Q000235:genetics / Q000502:physiology; D016297:Mutagenesis, Site-Directed; D020125:Mutation, Missense; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D011994:Recombinant Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D012623:Seawater / Q000382:microbiology*; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA
chemical_list: D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D012336:RNA, Ribosomal, 16S; D011994:Recombinant Proteins; D008291:Malate Dehydrogenase