Forces, Fluxes and the Control of Microbial Growth and Metabolism: The Twelfth Fleming Lecture

Kell, Douglas B.

doi:10.1099/00221287-133-7-1651

Cited by 20 publications

(13 citation statements)

References 87 publications

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“…A number of studies have shown that growth yields (grams of cell produced per mole of substrate consumed) are lower than predicted from considering the thermodynamics of the catabolic and anabolic events such that the ability to waste energy is intrinsic to cellular life, e.g., ref. [36][37][38]. However, growth yields have been found to vary in response to change of environment in a manner that suggests a key element of microbial respiration is the ability to spill, or dissipate, excess energy at a rate appropriate to the prevailing conditions.…”

Section: Electrochemical Potential As a Determinant Of Electron Flux mentioning

confidence: 99%

The relationship between redox enzyme activity and electrochemical potential—cellular and mechanistic implications from protein film electrochemistry

Gates

Kemp

et al. 2011

Phys. Chem. Chem. Phys.

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In protein film electrochemistry a redox protein of interest is studied as an electroactive film adsorbed on an electrode surface. For redox enzymes this configuration allows quantification of the relationship between catalytic activity and electrochemical potential. Considered as a function of enzyme environment, i.e., pH, substrate concentration etc., the activity-potential relationship provides a fingerprint of activity unique to a given enzyme. Here we consider the nature of the activity-potential relationship in terms of both its cellular impact and its origin in the structure and catalytic mechanism of the enzyme. We propose that the activity-potential relationship of a redox enzyme is tuned to facilitate cellular function and highlight opportunities to test this hypothesis through computational, structural, biochemical and cellular studies.

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Section: Electrochemical Potential As a Determinant Of Electron Flux mentioning

confidence: 99%

The relationship between redox enzyme activity and electrochemical potential—cellular and mechanistic implications from protein film electrochemistry

Gates

Kemp

et al. 2011

Phys. Chem. Chem. Phys.

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“…In metabolic control analysis, the extent to which an enzyme controls a flux, the enzyme's flux control coefficient (Burns e t al., 1985), is defined operationally as the percentage increase in flux resulting from a 1 % activation of the enzyme (Kell & Westerhoff, 1986;Kell, 1987). An important way experimentally to activate an enzyme is to enhance the expression of the corresponding gene so as to increase the concentration of the enzyme (Walsh & Koshland, 1985).…”

Section: Introductionmentioning

confidence: 99%

“…However, it was not substantiated that these processes had actual control over the aspect of cell function that was studied (usually growth rate). Koch (1983) concluded that permease insertion into the cytoplasmic membrane (for the case of the lac operon which has always been used as a model system) is deleterious and slows growth more than could be accounted for by the synthesis of unneeded protein.In metabolic control analysis, the extent to which an enzyme controls a flux, the enzyme's flux control coefficient (Burns e t al., 1985), is defined operationally as the percentage increase in flux resulting from a 1 % activation of the enzyme (Kell & Westerhoff, 1986;Kell, 1987). An important way experimentally to activate an enzyme is to enhance the expression of the corresponding gene so as to increase the concentration of the enzyme (Walsh & Koshland, 1985).…”

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confidence: 99%

Protein burden in Zymomonas mobilis: negative flux and growth control due to overproduction of glycolytic enzymes

et al. 1995

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Increasing the expression of various glycolytic operons in Zymomonss mobilis caused a significant decrease rather than increase in the glycolytic flux and growth rate. Because the relative decrease depended on the amount of overexpressed protein, and was independent of which enzyme was overexpressed, we attributed it to a protein burden effect. More specifically, we examined if the decrease in glycolytic flux could be explained by a decreased concentration of other glycolytic enzymes (for which glucokinase was used as a marker enzyme). Using the summation theorem of metabolic control theory we predicted the extent of this protein burden effect. The predictions were in good agreement with the experimental observations. This suggests that the negative flux control is caused either by a simple competition of the overexpressed gene with the expression of all other genes or by simple dilution. Furthermore, we determined the implications of protein burden for the determination of the extent to which an enzyme limits a flux. We conclude that a protein burden can cause a significant underestimation of the flux control coefficient, especially if the enzyme under investigation is a highly expressed enzyme.Keywords : protein burden, Zymomonas mobilis, flux control, glycolysis, metabolic control analysis INTRODUCTIONAttempts to optimize metabolic processes, by overexpression of enzymes that are thought to be important in the determination of the overall rate of formation of the desired product, often lead to negative results (Schaaff e t al., 1989;Niederberger et a/., 1992). This can be due to:(1) an intuitive overestimation of the actual importance of the enzyme in the production process -a clear distinction should be made between essential and controlling enzymes (Jensen e t a/., 1993a, b); (2) a shift of control upon overexpression (De Hollander, 1994;Small & Kacser, 1993); or (3) additional effects caused by the overexpression (Bailey, 1993). In the first case a quan- titative metabolic control analysis should lead to the identification of the enzymes that do exert flux control (Kacser & Burns, 1973;Heinrich & Rapoport, 1974; Groen e t a/., 1982; Fell, 1992). In the second case combined overexpression of a group (module, Schuster e t al., 1993) of enzymes should help (Small & Kacser, 1993). In the third case, the unspecific negative effects can be divided into energetic effects (costs to produce extra protein) and competitive effects (if the proteinsynthesizing machinery is limiting). In this paper we will use the term protein burden for the negative effect on any part of cell function caused by the overexpression of a protein independent of its catalytic activity. In order to evaluate the importance of an enzyme for the control of any flux under study, it is important to distinguish specific negative effects of the catalytic activity from this 'nonspecific ' protein burden. Thus, a quantitative analysis of the negative effects of expression of recombinant protein is needed. The protein burden effect has been recognize...

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“…It is interesting to note that a Mycobacterium strain with a slow growth rate has preferentially an NAD+-dependent malate dehydrogenase, in contrast to the membrane-bound FAD-linked malate dehydrogenase observed in a Mycobacterium strain with a high growth rate (Wheeler & Bharadwaj, 1983). One can assume that under non-limited growth of the obligate aerobe M. luteus the existence of the alternative, weakly coupled respiratory branch allows the cell to accelerate the rate of substrate oxidation coupled with ATP synthesis and/or substrate level phosphorylation (fast rate but low P/O ratio) (see Kell, 1987). …”

Section: Discussionmentioning

confidence: 99%

The increase of KCN-sensitive electron flow in the branched respiratory chain of Micrococcus luteus grown slowly in carbon-limited culture

Artzatbanov

Sheiko

Lukoyanova

et al. 1991

Journal of General Microbiology

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The strictly aerobic bacterium Micrococcus luteus was grown in the presence of lactate as sole carbon source under conditions of excess substrates (in batch culture) or under strict lactate (C) or ammonium (N) limitation (in a chemostat, D=O.O2 h-l). KCN (2mM) stimulated the respiration of batch-grown and N-limited cells, and inhibited the oxidase activity of C-limited cells by 4040%. The content and composition of dytochromes and the KCN-dependences of the oxidase activities were found to be the same for the membranes of C-limited and batchgrown cells. The KCN sensitivity of the oxidase activities of isolated membranes decreased in the order NADH > malate > lactate. NAD-dependent lactate and malate dehydrogenase activities were observed in the cytoplasm of C-limited cells but not in that of batch-grown cells. The stimulation of cell respiration by lactate, malate, pyruvate or ethanol caused a marked increase of the steady-state level of NAD+ reduction only in Climited cells. It is assumed that the slow growth of C-limited cells is accompanied by an increase in the formation of NADH, which is oxidized by the KCN-sensitive, tightly-coupled, main branch of the M. luteus respiratory chain. Under non-limited conditions of growth the respiration is due mainly to the direct oxidation of lactate via the weakly coupled alternative branch. The role of this switching of the electron flow from one pathway to the other during the adaptation of the bateria to the slow C-and energy-limited growth is discussed.

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Forces, Fluxes and the Control of Microbial Growth and Metabolism: The Twelfth Fleming Lecture

Cited by 20 publications

References 87 publications

The relationship between redox enzyme activity and electrochemical potential—cellular and mechanistic implications from protein film electrochemistry

The relationship between redox enzyme activity and electrochemical potential—cellular and mechanistic implications from protein film electrochemistry

Protein burden in Zymomonas mobilis: negative flux and growth control due to overproduction of glycolytic enzymes

The increase of KCN-sensitive electron flow in the branched respiratory chain of Micrococcus luteus grown slowly in carbon-limited culture

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