Lactate dehydrogenase fermentation

Yamada, T. and Carlsson, J. 1975A. Regulation of lactate dehydrogenase and change of fermentation products in streptococci. J. Bacteriol 124, 55-61. 

Dehydrogenases often act primarily to reduce a carbonyl compound rather than to dehydrogenate an alcohol. These enzymes may still be called dehydrogenases. For example, in the lactic acid fermentation lactate is formed by reduction of pyruvate but we still call the enzyme lactate dehydrogenase. In our bodies this enzyme functions in both directions. However, some enzymes that act mainly in the direction of reduction are called reductases. An example is aldose reductase, a member of a family of aldo-keto reductases71 73 which have (a / P)8-barrel structures.74 76... 

NAD-lactate dehydrogenase wines, ciders contamination fermentation process control... 

Fig. 5.4. Two types of energy metabolism in cestodes. (a) Type 1 homolactate fermentation, (b) Type 2 Malate dismutation. Reaction 3 involves a carboxylation step decarboxylation occurs at 6, 7 and 10. Reducing equivalents are generated at reactions 6 and 7 one reducing equivalent is used at reaction 9. Thus, when the mitochondrial compartment is in redox balance and malate is the sole substrate, twice as much propionate as acetate is produced. Key 1, pyruvate kinase 2, lactate dehydrogenase 3, phosphoenolpyruvate carboxykinase 4, malate dehydrogenase 5, mitochondrial membrane 6 malic enzyme 7, pyruvate dehydrogenase complex 8, fumarase 9, fumarate reductase 10, succinate decarboxylase complex. indicates reactions at which ATP is synthesised from ADP cyt, cytosol mit, mitochondrion. (After Bryant Flockhart, 1986.)...

This metabolic scheme, which is called lactate fermentation, is shown in Fig. 11-7. The coreactant cycle between the two dehydrogenase enzymes, glyceraldehyde-3-phosphate dehydrogenase (Step 6) and lactate dehydrogenase, ensures that there is regeneration of NAD+ in this particular oxidation state so that glycolysis, lactate fermentation, and the production of ATP can continue. 

Figure 16.12. Maintaining Redox Balance. The NADH produced by the glyceraldehyde 3-phosphate dehydrogenase reaction must be reoxidized to NAD+ for the glycolytic pathway to continue. In alcoholic fermentation, alcohol dehydrogenase oxidizes NADH and generates ethanol. In lactic acid fermentation (not shovm), lactate dehydrogenase oxidizes NADH while generating lactic acid.

Lactate dehydrogenase is closely associated with the final step in fermentative metabolism conversion of pyruvate to lactate- Citrate synthase is closely associated with oxidative metabolism, because this enzyme catalyzes the introduction of acetyl groups into the Krebs cycle. Continued operation of the Krebs cycle is dependent on the continued transfer of electrons from reduced NAD and FAD to the respiratory chain, which catalyzes the reduction of Oi to HjO. Table 4.14 lists lactate dehydrogenasc/citrate synthase activity ratios for muscles that contain a large proportion of white or red muscle fibers. The data demonstrate that the ratio is relatively high in white cell muscles but low in red cell muscles. 

Figure 1 Fermentation pathways of Escherichia coli. Gene symbols ackA, acetate kinase adhE, alcohol dehydrogenase fdh, formate dehydrogenase of FHL complex fhn, nitrate-inducible formate dehydrogenase hyd, hydrogenase 3 of FHL complex IdhA, NAD+-dependent D-(-)-lactate dehydrogenase pfl, pyruvate formate-lyase pta, phosphotransacetylase. FHL, formate hydrogenlyase. Redrawn from reference 29...

Sode, K., Watanabe, M., Makimoto, H. and Tomiyama, M. (1999). Construction and characterization of fermentative lactate dehydrogenase Escherichia coli mutant and its potential for bacterial hydrogen production. Appl. Biochem. Biotechnol. 77-79, 317-323. 

The production of, say, lactic acid from pyruvic acid is sometimes called homolactic fermentation. The enzyme involved in the one-step conversion is lactate dehydrogenase in one form or another. A schematic diagram for the conversion is shown in Figure 3.2. We omit further details about the conversion. 

The growth of microorganisms may have an important effect on the flavour of food. An example is the lactic acid bacteria Lactococcus lactis, which produce mainly lactate providing a characteristic acidic flavour and contributing to the preservation of fermented food. In an innovative approach, in situ 13C NMR was used to investigate glycolysis by an L. lactis strain deficient in lactate dehydrogenase.272... 

Using the same approach now in combination with a carbon paste electrode including D-lactate dehydrogenase, NAD" ", and a polymer-bound mediator, the concentration of D-lactate was followed during a fermentation [57, 58], This system is reagentless and the response was faster as compared to that of the enzyme reactor described above. In both cases it was shown that the selectivity of the enzyme was very good the only severely disturbing substance was pyruvate—the product of the reaction. 

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