Dehydrogenases mannitol dehydrogenase

Reductions catalyzed by glycerol dehydrogenase, sorbitol dehydrogenase, mannitol dehydrogenase, and aldose reductases formation of polyols from carbohydrates. 

Different preparative procedures have been shown to yield protein fractions which are able to catalyze different types of reactions with respect to their requirement of either NAD or NADP as coenzymes [cf. Eqs. (19), (20), and (21)]. In sera of mice poisoned by carbon tetrachloride we found polyol dehydrogenases catalyzing the oxidation of the following polyols (a) with NAD sorbitol, ribitol, mannitol (b) with NADP sorbitol, ribitol. Erythritol and mt/o-inositol were not attacked at all. Figures 8 and 9 show the results of these determinations performed at pH 9.6. In the NAD system sorbitol and ribitol are oxidized at exactly the same rate, while in the NADP system ribitol does not reach the rate of sorbitol. The ratio NAD NADP for sorbitol is calculated to be 4.20 and for ribitol 5.50. Mannitol is oxidized at 23% of the rate of sorbitol. 

Fic. 8. NAD polyol dehydrogenase in sera of CCl4-poisoned mice sorbitol, ribitol, and mannitol oxidation (pH 9.6 polyols as substrates). 

Sorbitol and Mannitol. Sorbitol is present in fruits but not in grapes. A method for its determination is required to detect illegal blending of fruit wines with grape wines. Mannitol is produced by bacterial spoilage. Sorbitol dehydrogenase and thin-layer chromatography have been used for their simultaneous determination (5). 

Several heterofermentative LAB belonging to the genera Lactobacillus, Leu-conostoc, and Oenococcus can produce mannitol from fructose effectively (Saha, 2003). In addition to mannitol, these bacteria may produce lactic acid, acetic acid, carbon dioxide, and ethanol. The process is based on the ability of the LAB to use fructose as an electron acceptor and reduce it to mannitol with the participation of the enzyme mannitol 2-dehydrogenase (EC 1.1.1.38). 

Several heterofermentative LAB produce mannitol in large amounts, using fructose as an electron acceptor. Mannitol produced by heterofermentative bacteria is derived from the hexose phosphate pathway (Soetaert et al., 1999 Wisselink et al., 2002). The process makes use of the capability of the bacterium to utilize fructose as an alternative electron acceptor, thereby reducing it to mannitol with the enzyme mannitol dehydrogenase. In this process, the reducing equivalents are generated by conversion of one-third fructose to lactic acid and acetic acid. The enzyme reaction proceeds according to (theoretical) Equation 21.1 ... 

Heterofermentative LAB have the capability to utilize high concentrations of fructose such that the mannitol concentration in the fermentation broth could reach more than 180g/L, which is enough to be separated from the cell-free fermentation broth by cooling crystallization. Lactic and acetic acids can be recovered by electrodialysis (Soetaert et al., 1995). The enzyme mannitol dehydrogenase responsible for catalyzing the conversion of fructose to mannitol requires NADPH (NADH) as cofactor. Thus, it is possible to develop a one-pot enzymatic process for production of mannitol from fructose if a cost-effective cofactor regeneration system can be developed (Saha, 2004). The heterofermentative LAB cells can be immobilized in a suitable support, and... 

Gaspar, P., Neves, A. R., Ramos, A., Gasson, M. J., Shearman, C. A., and Santos, H. 2004. Engineering Lactococcus lactis for production of mannitol high yields from food-grade strains deficient in lactate dehydrogenase and the mannitol transport system. App. Environ. Microbiol., 70,1466-1474. 

Hahn, G., Kaup, B., Bringer-Meyer, S., and Sahm, H. 2003. A zinc-containing mannitol-2-dehydrogenase from Leuconostoc pseudomesenteroides ATCC 12291 purification of the enzyme and cloning of the gene. Arch. Microbiol., 179,101-107. 

Liu, S., Saha, B., and Cotta, M. 2005. Cloning, expression, purification, and analysis of mannitol dehydrogenase gene mtlK from Lactobacillus brevis. Appl. Biochem. Biotechnol., 121-124, 391 102. 

Martinez, G. H., Barker, A., and Horecker, B. L. 1963. A specific mannitol dehydrogenase from Lactobacillus brevis. J. Biol. Chem., 238,1598-1603. 

Saha, B. C. 2004. Purification and characterization of a novel mannitol dehydrogenase from Lactobacillus intermedius. Biotechnol. Prog., 20,537-542. 

Sasaki, Y., Laivenieks, M., and Zeikus, J. G. 2005. Lactobacillus reuteri ATCC 53608 mdh gene cloning and recombinant mannitol dehydrogenase characterization. Appl. Microbiol. Biotechnol., 68, 36-41. 

Wisselink, H. W., Mars, A. E., van der Meer, P., Eggink, G, and Hugenholtz, J. 2004. Metabolic engineering of mannitol production in Lactococcus lactis influence of overexpression of mannitol-1-phosphate dehydrogenase in different genetic backgrounds. App. Environ. Microbiol., 76,4286 1292. 

EC 1.1.1.67 Mannitol 2-dehydrogenase fructose+nadred mannitolD-f nadox... 

Sum) or hollow spherical particles (such as sodium chloride, mannitol, or tobramycin sulfate) are formed depending on the compound. Protein powders such as lysozyme or lactate dehydrogenase can also be produced by this process and can be stabilized through the use of sugars, buffers, and surfactant additives in the formulations. Depending on the solute and conditions of drying, the particles are crystalline in some cases and amorphous in others. ° ... 

Lactate dehydrogenase phosphofructokinase Polyethylene glycol as protectant for freezing sugars (mannitol, lactose, trehalose) as lyoprotectants against loss of bioactivity [28]... 

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