title: Enzymatic characterization of 5-methylthioribose 1-phosphate isomerase from Bacillus subtilis.
abstract: The product of the mtnA gene of Bacillus subtilis catalyzes the isomerization of 5-methylthioribose 1-phosphate (MTR-1-P) to 5-methylthioribulose 1-phosphate (MTRu-1-P). The catalysis of MtnA is a novel isomerization of an aldose phosphate harboring a phosphate group on the hemiacetal group. This enzyme is distributed widely among bacteria through higher eukaryotes. The isomerase reaction analyzed using the recombinant B. subtilis enzyme showed a Michaelis constant for MTR-1-P of 138 microM, and showed that the maximum velocity of the reaction was 20.4 micromol min(-1) (mg protein)(-1). The optimum reaction temperature and reaction pH were 35 degrees C and 8.1. The activation energy of the reaction was calculated to be 68.7 kJ mol(-1). The enzyme, with a molecular mass of 76 kDa, was composed of two subunits. The equilibrium constant in the reversible isomerase reaction [MTRu-1-P]/[MTR-1-P] was 6. We discuss the possible reaction mechanism.
authors: Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma, Nara, Japan.
authors: Yohtaro
authors: Y
authors: Saito
authors: Hiroki
authors: H
authors: Ashida
authors: Chojiro
authors: C
authors: Kojima
authors: Haruka
authors: H
authors: Tamura
authors: Hiroyoshi
authors: H
authors: Matsumura
authors: Yasushi
authors: Y
authors: Kai
authors: Akiho
authors: A
authors: Yokota
mesh_terms: D019747:Aldose-Ketose Isomerases / Q000737:chemistry / Q000378:metabolism*; D001412:Bacillus subtilis / Q000201:enzymology*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D021122:Protein Subunits; D011994:Recombinant Proteins; D012267:Ribosemonophosphates / Q000378:metabolism; D012274:Ribulosephosphates / Q000378:metabolism; D013696:Temperature; D013816:Thermodynamics; D013865:Thioglycosides / Q000378:metabolism
chemical_list: C023029:5'-methylthioribose 1-phosphate; D021122:Protein Subunits; D011994:Recombinant Proteins; D012267:Ribosemonophosphates; D012274:Ribulosephosphates; D013865:Thioglycosides; C038238:1-phospho-5-S-methylthioribulose; C056455:1-phospho-5-S-methylthioribofuranoside isomerase; D019747:Aldose-Ketose Isomerases