Home  About us  Contact
 

Hyperthermophilic Bacterium Thermotoga Maritima (hyperthermophilic + bacterium_thermotoga_maritima)

Distribution by Scientific Domains
Chemistry66%

Selected Abstracts

Characterization and mode of action of an exopolygalacturonase from the hyperthermophilic bacterium Thermotoga maritima

FEBS JOURNAL, Issue 21 2005
Leon D. Kluskens
An intracellular pectinolytic enzyme, PelB (TM0437), from the hyperthermophilic bacterium Thermotoga maritima was functionally produced in Escherichia coli and purified to homogeneity. PelB belongs to family 28 of the glycoside hydrolases, consisting of pectin-hydrolysing enzymes. As one of the few bacterial exopolygalacturonases, it is able to remove monogalacturonate units from the nonreducing end of polygalacturonate. Detailed characterization of the enzyme showed that PelB is highly thermo-active and thermostable, with a melting temperature of 105 °C and a temperature optimum of 80 °C, the highest described to date for hydrolytic pectinases. PelB showed increasing activity on oligosaccharides with an increasing degree of polymerization. The highest activity was found on the pentamer (1000 U·mg,1). In addition, the affinity increased in conjunction with the length of the oligoGalpA chain. PelB displayed specificity for saturated oligoGalpA and was unable to degrade unsaturated or methyl-esterified oligoGalpA. Analogous to the exopolygalacturonase from Aspergillus tubingensis, it showed low activity with xylogalacturonan. Calculations on the subsite affinity revealed the presence of four subsites and a high affinity for GalpA at subsite +1, which is typical of exo-active enzymes. The physiological role of PelB and the previously characterized exopectate lyase PelA is discussed. [source]

Glucose-6-phosphate dehydrogenase from the hyperthermophilic bacterium Thermotoga maritima: expression of the g6pd gene and characterization of an extremely thermophilic enzyme

FEMS MICROBIOLOGY LETTERS, Issue 2 2002
Thomas Hansen
Abstract The gene (open reading frame Tm1155, g6pd) encoding glucose-6-phosphate dehydrogenase (G6PD, EC 1.1.1.49) of the hyperthermophilic bacterium Thermotoga maritima was cloned and functionally expressed in Escherichia coli. The purified recombinant enzyme is a homodimer with an apparent molecular mass of 95 kDa composed of 60-kDa subunits. Rate dependence (at 80°C) on glucose-6-phosphate and NADP+ followed Michaelis,Menten kinetics with apparent Km values of 0.15 mM and 0.03 mM, respectively; apparent Vmax values were about 20 U mg,1. The enzyme also reduced NAD+ (apparent Km 12 mM, Vmax 12 U mg,1). The 1000-fold higher catalytic activity (kcat/Km) with NADP+ over NAD+ defines the G6PD as NADP+ specific in vivo. G6PD activity was competitively inhibited by NADPH with a Ki value of 0.11 mM. With a temperature optimum of 92°C the enzyme is the most thermoactive G6PD described. [source]

Structure of a d -tagatose 3-epimerase-related protein from the hyperthermophilic bacterium Thermotoga maritima

ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 3 2009
Haruhiko Sakuraba
The crystal structure of a d -tagatose 3-epimerase-related protein (TM0416p) encoded by the hypothetical open reading frame TM0416 in the genome of the hyperthermophilic bacterium Thermotoga maritima was determined at a resolution of 2.2,Å. The asymmetric unit contained two homologous subunits and a dimer was generated by twofold symmetry. The main-chain coordinates of the enzyme monomer proved to be similar to those of d -tagatose 3-epimerase from Pseudomonas cichorii and d -psicose 3-epimerase from Agrobacterium tumefaciens; however, TM0416p exhibited a unique solvent-accessible substrate-binding pocket that reflected the absence of an ,-helix that covers the active-site cleft in the two aforementioned ketohexose 3-epimerases. In addition, the residues responsible for creating a hydrophobic environment around the substrate in TM0416p differ entirely from those in the other two enzymes. Collectively, these findings suggest that the substrate specificity of TM0416p is likely to differ substantially from those of other d -tagatose 3-epimerase family enzymes. [source]