Previous Article | Next Article 
Journal of Bacteriology, September 1999, p. 5521-5526, Vol. 181, No. 17
Microbial Ingredients Section, NIZO Food
Research and Wageningen Centre for Food Science, 6710 BA Ede, The
Netherlands1; Laboratoire de
Génétique Moléculaire, Université catholique de
Louvain, B-1348 Louvain-La-Neuve, Belgium2; and
Instituto de Biologia Experimental e Tecnológica,
Instituto de Tecnologia Química e Biológica, Universidade
Nova de Lisboa, 2780 Oeiras, Portugal3
Received 8 March 1999/Accepted 27 June 1999
Acetate was shown to improve glucose fermentation in
Lactococcus lactis deficient in lactate dehydrogenase.
13C and 1H nuclear magnetic resonance studies
using [2-13C]glucose and [2-13C]acetate as
substrates demonstrated that acetate was exclusively converted to
ethanol. This novel pathway provides an alternative route for
NAD+ regeneration in the absence of lactate dehydrogenase.
Lactococcus lactis is a
lactic acid bacterium of major importance in the manufacture of dairy
products. This bacterium displays an exclusive fermentative metabolism
under dairy fermentation conditions: sugars are first converted by the
Embden-Meyerhof-Parnas pathway to pyruvate, which is further reduced
into L-lactate by an L-lactate dehydrogenase
(L-LDH) (homolactic fermentation). The ATP is mainly
produced (2 mol of ATP per mol of glucose) through glycolysis by
substrate-level phosphorylation. A strict balance in the
NADH/NAD+ ratio is maintained: the NAD+
cofactor reduced during glycolysis is regenerated during pyruvate reduction by the L-LDH (5).
A shift from the homolactic fermentation to a mixed-acid fermentation
has been observed under certain conditions, such as carbohydrate
limitation (21), galactose utilization (7, 22) or
aerobic conditions (3). Besides L-LDH, three
enzymes are able to dissipate pyruvate under different physiological
conditions (reviewed in reference 10) (Fig.
1). The first is
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Acetate Utilization in Lactococcus
lactis Deficient in Lactate Dehydrogenase: a Rescue Pathway for
Maintaining Redox Balance
ABSTRACT
Top
Abstract
Text
References
TEXT
Top
Abstract
Text
References
-acetolactate synthase (ALS), which is active at a high pyruvate concentration and a
low pH. Dissipation of pyruvate through this pathway can produce
acetoin, diacetyl, and 2,3-butanediol. The second is the pyruvate
dehydrogenase complex, which is active in aerobic conditions and at low
pH and is inhibited at high NADH concentrations. The end products from
this pathway are acetate and/or ethanol. The third is pyruvate
formate-lyase, which is active under anaerobic conditions and at high
pH. The end products are in this case a mixture of formate, acetate,
and/or ethanol.
View larger version (32K):
[in a new window]
FIG. 1.
Schematic pathways of glucose and acetate cometabolism
in L-LDH-deficient L. lactis. The proposed
pathway of acetate conversion to ethanol and its coupling to glycolysis
for cofactor regeneration is highlighted (grey area). Reactions or
pathways producing NADH are denoted by large black arrows, those that
are NADH independent are denoted by thin black arrows, and those
producing NAD+ are denoted by large white arrows. The fate
of the label derived from [2-13C]glucose and
[2-13C]acetate (shaded region) is shown. ACK, acetate
kinase; ADC, -acetolactate decarboxylase; ADH, acetaldehyde/alcohol
dehydrogenase; A/DR, -acetolactate/diacetyl reductase; NOX, NADH
oxidase; ODC, oxidative decarboxylation (chemical reaction); PDHC,
pyruvate dehydrogenase complex; PFL, pyruvate/formate lyase; PTA,
phosphotransacetylase; ?, unknown enzyme(s) involved in residual
lactate production.
Under aerobic conditions, mixed-acid fermentation was shown to mainly result from the activation of an H2O-forming NADH oxidase (13) which strongly lowered the pool of NADH available for L-LDH, leading to a rerouting of pyruvate through the other aerobic catabolic pathways. The importance of NADH oxidase in controlling the NADH/NAD+ balance was recently exploited as a novel metabolic engineering strategy (cofactor engineering) in L. lactis (14). Overproduction of NADH oxidase resulted in the complete replacement of lactate by a mixture of acetate and acetoin (14). In this situation, all NADH-dependent enzymes were inhibited and the pyruvate pool was rerouted toward oxidative or NADH-independent pathways.
Platteeuw et al. (16) reported the various end products of sugar fermentation obtained with growing cells of an L-LDH-deficient strain. Under anaerobic conditions (initial pH 6.0), these are mainly a mixture of formate (34% of lactose utilization), ethanol (28%), acetoin (11%), and 2,3-butanediol (22%). Under aerobic conditions (initial pH 6.0), a mixture of acetoin (52%), 2,3-butanediol (31.5%), and ethanol (17%) was observed. Surprisingly, the production of acetate in both conditions was less than 2%. Therefore, the L-LDH-deficient strain was suspected to use acetate as an exogenous electron acceptor, as was reported for the metabolism of sorbitol and mannitol by lactobacilli (15, 20).
This paper reports the cometabolism of acetate and glucose in an L-LDH-deficient strain of L. lactis in which acetate is exclusively converted to ethanol, providing an alternative pathway for NAD+ regeneration.
End product formation from glucose-acetate cometabolism by an
L-LDH-deficient strain.
Metabolic studies were
performed with buffered cell suspensions, which greatly facilitate end
product analysis. The L. lactis cells grown in GM17 (M17
medium [Merck] supplemented with 0.5% [wt/vol] glucose) were
collected at an optical density at 600 nm of 2.0, washed, and
resuspended at a concentration of approximately 3.3 g (dry weight)
per liter in 100 mM KH2PO4-100 mM
Na2HPO4 (pH 7.0) buffer supplemented with
glucose (50 mM) and/or ammonium acetate (100 mM). The cell suspensions
were incubated under low- or high-aeration conditions by shaking the
cells either in 10-ml tubes at 50 rpm (Table
1, low aeration) or in 30-ml tubes at 200 rpm (Table 1, high aeration) in an upright position in a G76 waterbath
(New Brunswick Scientific, Edison, N.J.). The supernatant (4 ml) was
recovered after 1 h of incubation at 30°C, and end products were
analyzed by high-pressure liquid chromatography (HPLC) (19)
except -acetolactate and acetoin, which were determined by using
chemical assays (24).
|
lacF ldh
pepN::nisRK]; MG1363 derivative
[9]) resulted in a mixed-acid fermentation (Table 1)
as observed previously by Platteeuw et al. for growing cells
(16). However, at a low aeration rate, glucose consumption
was threefold lower than in the wild-type strain (NZ3900
[lacF pepN::nisRK];
MG1363 derivative [4]); pyruvate was mainly rerouted
toward the ALS pathway (41.5% of glucose utilization) as expected, but
acetate and ethanol were not detected, and a significant amount
(12.8%) of pyruvate was excreted. At a high aeration rate, glucose
consumption was significantly higher and the expected distribution of
end products, including acetate (9.1%) and ethanol (12.6%), was
observed as previously reported for growing cells (16).
Excretion of pyruvate by the L-LDH-deficient strain could
easily be explained by a low efficiency of the alternative
pyruvate-dissipating enzymes at a low aeration rate and a high initial
pH (7.0), as indicated above. The low level of glucose consumption
probably resulted from an inefficient regeneration of NAD+
since the acetoin pathway (via ALS) is NADH independent and
NAD+ regeneration by NADH oxidase is not fully operative.
At a higher aeration rate, the NADH oxidase activity is enhanced,
resulting in an increased regeneration of NAD+ (favoring
glycolysis) and a decreased inhibition of the (pyruvate dehydrogenase
complex by a high NADH concentration (allowing the production of
acetate and ethanol).
The addition of acetate to cell suspensions of the
L-LDH-deficient strain at low aeration rates resulted in a
nearly equimolar consumption of glucose and acetate (acetate/glucose
ratio of 0.84), while no acetate was consumed by cell suspensions of
the wild-type strain under the same conditions (Table 1). Furthermore,
glucose was consumed to an extent similar to that for the wild-type
strain, and ethanol was produced at a level nearly equimolar to that of acetate utilization (acetate/ethanol ratio of 0.95). These observations suggested that the most probable pathway of conversion of acetate to
ethanol is as presented in Fig. 1. In this scheme, acetate is first
converted to acetyl coenzyme A (acetyl-CoA) by acetate kinase and
phosphotransacetylase, and acetyl-CoA is next reduced to ethanol by
alcohol dehydrogenase with a concomitant oxidation of 2 mol of NADH to
NAD+. This pathway enables a coupling of acetate
utilization (1 acetate + 2 NADH + 1 ATP 
1 ethanol + 2 NAD+ + 1 ADP + 1 Pi) to glycolysis
(glucose + 2 NAD+ + 2 ADP + 2 Pi
2 pyruvate + 2 NADH + 2 ATP) and cofactor regeneration. The acetate pathway also consumes 1 mol of ATP per mol of acetate, which could eventually improve the ATP turnover by stimulating glycolytic enzymes (pyruvate kinase and phosphofructokinase) and thus
favoring glucose utilization. However, acetate metabolism at a high
aeration rate does not improve glucose utilization in contrast to
low-aeration conditions. At a high aeration rate, high glucose
consumption correlates with activation of the NADH oxidase, which plays
a crucial role in maintaining an equilibrated redox balance without any
direct impact on ATP turnover. Table 1 shows that glucose-acetate
cometabolism in the L-LDH-deficient strain at a high
aeration rate results in a lower utilization of acetate
(acetate/glucose ratio of 0.35) than in low-aeration conditions
(acetate/glucose ratio of 0.84). These observations could be explained
by a different level of competition for NADH between the NADH oxidase
and the acetate utilization pathway (Fig. 1), which plays a predominant
role in NAD+ regeneration rather than in ATP turnover.
Analysis of glucose-acetate cometabolism by 13C and 1H NMR. Nuclear magnetic resonance spectroscopy (NMR) was used to test the hypothesis that acetate was converted to ethanol in the L-LDH-negative strain of L. lactis. NMR is a powerful technique for studying metabolic pathways since the use of 13C-labeled substrates allows evaluation of the fate of individual carbon atoms in a noninvasive way (12, 23). Furthermore, when a mixture of selectively enriched substrates is used (mixotrophic conditions), the origin of the carbon atoms in the end products formed can be determined by analysis of their labeling patterns (17, 18). In our experiments, a mixture of glucose labeled on C-2 and acetate labeled on the methyl group was supplied to the cells. The fate of each substrate can be determined easily from analysis of the isotopic enrichment in the two carbon atoms of ethanol. In fact, the label would end on the methylene group if ethanol were derived from glucose and on the methyl group if it were derived from acetate. This approach provided a definite proof for the operation of the pathway converting acetate to ethanol.
As for the previous studies, fermentation was performed with resting cells. L. lactis cells were harvested in the mid-exponential growth phase, washed, and resuspended at a concentration of approximately 20 g (dry weight) per liter in potassium phosphate buffer (50 mM, pH 5.5) supplemented with [2-13C]glucose (40 mM) and [2-13C]acetate (sodium salt, 40 mM). The supernatant was recovered for end product analysis by NMR following 1 h of incubation at 30°C. Figure 2A shows the 13C NMR spectrum of the supernatant containing the end products of [2-13C]acetate and [2-13C]glucose cometabolism by the L-LDH-deficient strain at pH 5.5. Catabolism of [2-13C]glucose produced acetoin labeled on the CO and CHOH groups, 2,3-butanediol labeled on both CHOH groups, acetate labeled on the COOH group, ethanol labeled on the CH2OH group, and a small amount of lactate enriched on the CHOH group (Fig. 1 and 2A). These end products were as expected from a fermentation performed in the presence of oxygen at low pH. The production of 2,3-butanediol in these conditions was reported previously by Platteeuw et al. (16). On the other hand, no pyruvate was detected, which suggested a better efficiency of pyruvate-dissipating enzymes at low pH, as previously reported for the ALS enzyme (10, 16).
|
= 23.6 ppm) was due to the methyl group of residual [2-13C]acetate.
Ethanol was the only metabolite produced from the supplied acetate,
since no other resonances with a labeling pattern consistent with
derivation from 13CH3 acetate were observed in
the spectrum. This observation was confirmed by analysis of the proton
spectrum (Fig. 2B). The resonance patterns due to the methyl groups of
acetate and ethanol are highlighted in Fig. 2B. The central resonance
at 1.9 ppm in the acetate pattern is assigned to unlabeled acetate, the
low-intensity inner doublet is due to
CH313COO
(derived from glucose),
and the high-intensity lateral resonance split by a coupling constant
of 127 Hz is due to the added
13CH3COO that remained in the
supernatant. The ethanol derived from [2-13C]acetate,
labeled on the CH3 group, originates the doublet of triplets clearly observed at a higher field in the ethanol pattern, while ethanol derived from glucose metabolism was not clearly detected
on this spectrum. Integration of the areas of these resonances allowed
us to determine that 12.5 mM ethanol was produced from [2-13C]acetate metabolism. The resonances due to other
products of glucose metabolism (acetoin and 2,3-butanediol) are also
identified in Fig. 2B.
13C and 1H NMR analysis of the supernatant
resulting from the metabolism of [2-13C]glucose and
[2-13C]acetate by the wild-type strain at pH 5.5 showed
that acetate was not metabolized and that glucose was completely
converted to lactate (data not shown).
Concluding remarks.
Acetate is cometabolized with glucose
under various conditions of aeration and initial pH only when the
L-LDH is inactivated in L. lactis. Acetate is
exclusively converted into ethanol, as demonstrated by NMR analysis. A
hypothetical acetate-ethanol pathway is presented in Fig. 1. This
pathway suggests acetyl-CoA, not pyruvate, as an intermediate, since no
product other than ethanol was detected from acetate metabolism.
Acetate is proposed to be converted to acetyl-CoA by the acetate
kinase-phosphotransacetylase pathway via acetyl-P, since both enzymatic
activities have been found in L. lactis (10).
However, we cannot exclude the possibility that acetate can be
partially or totally converted to acetyl-CoA by an acetyl-CoA synthase
enzyme (acetate + ATP + CoA acetyl-CoA + AMP + PPi) as reported for other bacteria (2, 6, 8), although this activity has not been reported for L. lactis.
The conversion of acetyl-CoA to ethanol is known to take place in L. lactis via a bifunctional alcohol dehydrogenase enzyme
whose genetic inactivation is responsible for a strong reduction in ethanol production (1). This last reaction is responsible
for NAD+ regeneration, thus allowing glucose metabolism
through glycolysis in an L-LDH-negative strain in the
absence of efficient reductive pathways. The role of the NADH oxidase
in improving and/or modifying the redox balance is well known (13,
14). This newly described pathway performs a similar function and
reinforces the predominant role of the NADH/NAD+ ratio in
governing the glycolytic flux and the distribution of fermentation end
products in L. lactis. Furthermore, one of the consequences
of glucose-acetate cometabolism is the unexpected excretion of a large
quantity of pyruvate (up to 34%), which is a key intermediate
metabolite, now available to be rerouted by metabolic engineering
toward new pathways unable to regenerate NAD+.
| |
ACKNOWLEDGMENTS |
|---|
This research was carried out in the framework of the European Community Research Programme BIOTECH (contract BIO4-CT96-0498). P.H. holds an EC BIOTECH postdoctoral training grant (contract BIO4-CT96-5093). A.R. is grateful to Fundação de Ciência e Tecnologia, Portugal, for a postdoctoral fellowship.
We thank R. Holleman for technical help in HPLC analyses.
| |
FOOTNOTES |
|---|
* Corresponding author. Mailing address: Laboratoire de Génétique Moléculaire, Université catholique de Louvain, 5 Place Croix du Sud, B-1348 Louvain-La-Neuve, Belgium. Phone: 32-10-478896. Fax: 32-10-473109. E-mail: hols{at}gene.ucl.ac.be.
| |
REFERENCES |
|---|
|
Top
Abstract
Text
References
|
|---|
| 1. |
Arnau, J.,
F. Jørgensen,
S. M. Madsen,
A. Vrang, and H. Israelsen.
1998.
Cloning of the Lactococcus lactis adhE gene, encoding a multifunctional alcohol dehydrogenase, by complementation of a fermentative mutant of Escherichia coli.
J. Bacteriol.
180:3049-3055 |
| 2. |
Brown, T. D. K.,
M. C. Jones-Mortimer, and H. L. Kornberg.
1977.
The enzymatic interconversion of acetate and acetyl-coenzyme A in Escherichia coli.
J. Gen. Microbiol.
102:327-336 |
| 3. | Condon, S. 1987. Responses of lactic acid bacteria to oxygen. FEMS Microbiol. Rev. 46:269-280. |
| 4. | de Ruyter, P. G. G. A., O. P. Kuipers, and W. M. de Vos. 1996. Controlled gene expression systems for Lactococcus lactis with the food-grade inducer nisin. Appl. Environ. Microbiol. 62:3662-3667[Abstract]. |
| 5. | de Vos, W. M. 1996. Metabolic engineering of sugar catabolism in lactic acid bacteria. Antonie Leeuwenhoek 70:223-242. |
| 6. |
Eggen, R. I. L.,
A. C. M. Geerling,
A. B. P. Boshoven, and W. M. de Vos.
1991.
Cloning, sequence analysis, and functional expression of the acetyl coenzyme A synthetase gene from Methanothrix soehngenii in Escherichia coli.
J. Bacteriol.
173:6383-6389 |
| 7. |
Garrigues, C.,
P. Loubiere,
N. D. Lindley, and M. Cocaign-Bousquet.
1997.
Control of the shift from homolactic acid to mixed-acid fermentation in Lactococcus lactis: predominant role of the NADH/NAD+ ratio.
J. Bacteriol.
179:5282-5287 |
| 8. | Grundy, F. J., D. A. Waters, T. Y. Takova, and T. M. Henkin. 1993. Identification of genes involved in utilization of acetate and acetoin in Bacillus subtilis. Mol. Microbiol. 10:259-271[Medline]. |
| 9. | Hols, P., M. Kleerebezem, A. N. Schanck, T. Ferain, J. Hugenholtz, J. Delcour, and W. M. de Vos. 1999. Conversion of Lactococcus lactis from homolactic to homoalanine fermentation through metabolic engineering. Nat. Biotechnol. 17:588-592. [Medline] |
| 10. | Hugenholtz, J. 1993. Citrate metabolism in lactic acid bacteria. FEMS Microbiol. Rev. 12:165-178. |
| 11. | Lees, G. J. 1976. Acetaldehyde: an intermediate in the formation of ethanol from glucose by lactic acid bacteria. J. Dairy Res. 43:63-73[Medline]. |
| 12. | London, R. E. 1988. 13C labelling studies of metabolic regulation. Prog. Nucl. Magn. Reson. Spectrosc. 20:337-383. |
| 13. | Lopez de Felipe, F., M. J. C. Starrenburg, and J. Hugenholtz. 1997. The role of NADH-oxidation in acetoin and diacetyl production from glucose in Lactococcus lactis. FEMS Microbiol. Lett. 156:15-19. |
| 14. |
Lopez de Felipe, F.,
M. Kleerebezem,
W. M. de Vos, and J. Hugenholtz.
1998.
Cofactor engineering: a novel approach to metabolic engineering in Lactococcus lactis by controlled expression of NADH oxidase.
J. Bacteriol.
180:3804-3808 |
| 15. | McFeeters, R. F., and K.-H. Chen. 1986. Utilization of electron acceptors for anaerobic mannitol metabolism by Lactobacillus plantarum. Compounds which serve as electron acceptors. Food Microbiol. 3:73-81. |
| 16. |
Platteeuw, C.,
J. Hugenholtz,
M. Starrenburg,
I. van Alen-Boerrigter, and W. M. de Vos.
1995.
Metabolic engineering of Lactococcus lactis: influence of the overproduction of -acetolactate synthase in strains deficient in lactate dehydrogenase as a function of culture conditions.
Appl. Environ. Microbiol.
61:3967-3971[Abstract].
|
| 17. |
Ramos, A.,
K. N. Jordan,
T. M. Cogan, and H. Santos.
1994.
13C nuclear magnetic resonance studies of citrate and glucose cometabolism by Lactococcus lactis.
Appl. Environ. Microbiol.
60:1739-1748 |
| 18. | Ramos, A., and H. Santos. 1996. Citrate and sugar cofermentation in Leuconostoc oenos, a 13C nuclear magnetic resonance study. Appl. Environ. Microbiol. 62:2577-2585[Abstract]. |
| 19. |
Starrenburg, M. J. C., and J. Hugenholtz.
1991.
Citrate fermentation by Lactococcus and Leuconostoc spp.
Appl. Environ. Microbiol.
57:3535-3540 |
| 20. | Takahashi, N., S. Kalfas, and T. Yamada. 1995. Effect of acetate on sorbitol fermentation by oral lactobacilli. Oral Microbiol. Immunol. 10:349-354[Medline]. |
| 21. |
Thomas, T. D.,
D. C. Ellwood, and V. M. C. Longyear.
1979.
Change from homo- to heterolactic fermentation by Streptococcus lactis resulting from glucose limitation in anaerobic chemostat cultures.
J. Bacteriol.
138:109-117 |
| 22. |
Thomas, T. D.,
K. W. Turner, and V. L. Crow.
1980.
Galactose fermentation by Streptococcus lactis and Streptococcus cremoris: pathways, products, and regulation.
J. Bacteriol.
144:672-682 |
| 23. |
Veiga-da-Cunha, M.,
P. Firme,
M. V. San Romão, and H. Santos.
1992.
Application of 13C nuclear magnetic resonance to elucidate the unexpected biosynthesis of erythritol by Leuconostoc oenos.
Appl. Environ. Microbiol.
58:2271-2279 |
| 24. |
Veringa, H. A.,
E. H. Verburg, and J. Stadhouders.
1984.
Determination of diacetyl in dairy products containing -acetolactic acid.
Neth. Milk Dairy J.
38:251-263.
|
Journal of Bacteriology, September 1999, p. 5521-5526, Vol. 181, No. 17
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
This article has been cited by other articles:
-
Ladero, V., Ramos, A., Wiersma, A., Goffin, P., Schanck, A., Kleerebezem, M., Hugenholtz, J., Smid, E. J., Hols, P.
(2007). High-Level Production of the Low-Calorie Sugar Sorbitol by Lactobacillus plantarum through Metabolic Engineering. Appl. Environ. Microbiol.
73: 1864-1872
[Abstract] [Full Text] -
Bongers, R. S., Hoefnagel, M. H. N., Kleerebezem, M.
(2005). High-Level Acetaldehyde Production in Lactococcus lactis by Metabolic Engineering. Appl. Environ. Microbiol.
71: 1109-1113
[Abstract] [Full Text] -
Gaspar, P., Neves, A. R., Ramos, A., Gasson, M. J., Shearman, C. A., 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. Appl. Environ. Microbiol.
70: 1466-1474
[Abstract] [Full Text] -
Bongers, R. S., Hoefnagel, M. H. N., Starrenburg, M. J. C., Siemerink, M. A. J., Arends, J. G. A., Hugenholtz, J., Kleerebezem, M.
(2003). IS981-Mediated Adaptive Evolution Recovers Lactate Production by ldhB Transcription Activation in a Lactate Dehydrogenase-Deficient Strain of Lactococcus lactis. J. Bacteriol.
185: 4499-4507
[Abstract] [Full Text] -
Nordkvist, M., Jensen, N. B. S., Villadsen, J.
(2003). Glucose Metabolism in Lactococcus lactis MG1363 under Different Aeration Conditions: Requirement of Acetate To Sustain Growth under Microaerobic Conditions. Appl. Environ. Microbiol.
69: 3462-3468
[Abstract] [Full Text] -
Neves, A. R., Ramos, A., Costa, H., van Swam, I. I., Hugenholtz, J., Kleerebezem, M., de Vos, W., Santos, H.
(2002). Effect of Different NADH Oxidase Levels on Glucose Metabolism by Lactococcus lactis: Kinetics of Intracellular Metabolite Pools Determined by In Vivo Nuclear Magnetic Resonance. Appl. Environ. Microbiol.
68: 6332-6342
[Abstract] [Full Text] -
Lynd, L. R., Weimer, P. J., van Zyl, W. H., Pretorius, I. S.
(2002). Microbial Cellulose Utilization: Fundamentals and Biotechnology. Microbiol. Mol. Biol. Rev.
66: 506-577
[Abstract] [Full Text] -
Neves, A. R., Ventura, R., Mansour, N., Shearman, C., Gasson, M. J., Maycock, C., Ramos, A., Santos, H.
(2002). Is the Glycolytic Flux in Lactococcus lactis Primarily Controlled by the Redox Charge? KINETICS OF NAD+ AND NADH POOLS DETERMINED IN VIVO BY 13C NMR. J. Biol. Chem.
277: 28088-28098
[Abstract] [Full Text]
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Copyright © 2009 by the American Society for Microbiology. For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»