Enzymatic characterization of 5-methylthioribose 1-phosphate isomerase from Bacillus subtilis.
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.
Saito
Yohtaro
Y
Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma, Nara, Japan.
Ashida
Hiroki
H
Kojima
Chojiro
C
Tamura
Haruka
H
Matsumura
Hiroyoshi
H
Kai
Yasushi
Y
Yokota
Akiho
A
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
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