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13 Publications visible to you, out of a total of 13
Inhibitor titrations reveal low control of glyceraldehyde 3-phosphate dehydrogenase and high control of hexokinase on glycolytic flux in an aggressive triple-negative breast cancer cell line

Abstract

Not specified

Authors: Theresa Kouril, Craig October, Stephanie Hollocks, Christoff Odendaal, David D. van Niekerk, Jacky L. Snoep

Date Published: 1st Sep 2023

Publication Type: Journal

A combined experimental and modelling approach for the Weimberg pathway optimisation

Abstract (Expand)

The oxidative Weimberg pathway for the five-step pentose degradation to α-ketoglutarate is a key route for sustainable bioconversion of lignocellulosic biomass to added-value products and biofuels. The … oxidative pathway from Caulobacter crescentus has been employed in in-vivo metabolic engineering with intact cells and in in-vitro enzyme cascades. The performance of such engineering approaches is often hampered by systems complexity, caused by non-linear kinetics and allosteric regulatory mechanisms. Here we report an iterative approach to construct and validate a quantitative model for the Weimberg pathway. Two sensitive points in pathway performance have been identified as follows: (1) product inhibition of the dehydrogenases (particularly in the absence of an efficient NAD+ recycling mechanism) and (2) balancing the activities of the dehydratases. The resulting model is utilized to design enzyme cascades for optimized conversion and to analyse pathway performance in C. cresensus cell- free extracts.

Authors: Lu Shen, Martha Kohlhaas, Junichi Enoki, Roland Meier, Bernhard Schönenberger, Roland Wohlgemuth, Robert Kourist, Felix Niemeyer, David van Niekerk, Christopher Bräsen, Jochen Niemeyer, Jacky Snoep, Bettina Siebers

Date Published: 1st Dec 2020

Publication Type: Not specified

Phosphofructokinase controls the acetaldehyde-induced phase shift in isolated yeast glycolytic oscillators

Abstract (Expand)

Abstract The response of oscillatory systems to external perturbations is crucial for emergent properties such as synchronisation and phase locking and can be quantified in a phase response curve (PRC). …hase response curve (PRC). In individual, oscillating yeast cells, we characterised experimentally the phase response of glycolytic oscillations for external acetaldehyde pulses and followed the transduction of the perturbation through the system. Subsequently, we analysed the control of the relevant system components in a detailed mechanistic model. The observed responses are interpreted in terms of the functional coupling and regulation in the reaction network. We find that our model quantitatively predicts the phase-dependent phase shift observed in the experimental data. The phase shift is in agreement with an adaptation leading to synchronisation with an external signal. Our model analysis establishes that phosphofructokinase plays a key role in the phase shift dynamics as shown in the PRC and adaptation time to external perturbations. Specific mechanism-based interventions, made possible through such analyses of detailed models, can improve upon standard trial and error methods, e.g. melatonin supplementation to overcome jet-lag, which are error-prone, specifically, since the effects are phase dependent and dose dependent. The models by Gustavsson and Goldbeter discussed in the text can be obtained from the JWS Online simulation database: (https://jjj.bio.vu.nl/models/gustavsson5 and https://jjj.bio.vu.nl/models/goldbeter1)

Authors: David D. van Niekerk, Anna-Karin Gustavsson, Martin Mojica-Benavides, Caroline B. Adiels, Mattias Goksör, Jacky L. Snoep

Date Published: 31st Jan 2019

Publication Type: Journal

11-Oxygenated androgen precursors are the preferred substrates for aldo-keto reductase 1C3 (AKR1C3): Implications for castration resistant prostate cancer

Abstract (Expand)

The progression of castration resistant prostate cancer (CRPC) is driven by the intratumoral conversion of adrenal androgen precursors to potent androgens. The expression of aldo-keto reductase 1C3 … (AKR1C3), which catalyses the reduction of weak androgens to more potent androgens, is significantly increased in CRPC tumours. The oxidation of androgens to their inactive form is catalysed by 17β-hydroxysteroid dehydrogenase type 2 (17βHSD2), but little attention is given to the expression levels of this enzyme. In this study, we show that the 11-oxygenated androgen precursors of adrenal origin are the preferred substrate for AKR1C3. In particular we show that the enzymatic efficiency of AKR1C3 is 8- and 24-fold greater for 11-ketoandrostenedione than for the classic substrates androstenedione and 5α-androstanedione, respectively. Using three independent experimental systems and a computational model we subsequently show that increased ratios of AKR1C3:17βHSD2 sig- nificantly favours the flux through the 11-oxygenated androgen pathway as compared to the classical or 5α- androstanedione pathways. Our findings reveal that the flux through the classical and 5α-androstanedione pathways are limited by the low catalytic efficiently of AKR1C3 towards classical androgens combined with the high catalytic efficiency of 17βHSD2, and that the expression of the oxidative enzyme therefore plays a vital role in determining the steady state concentration of active androgens. Using microarray data from prostate tissue we confirm that the AKR1C3:17βHSD2 ratio is significantly increased in patients undergoing androgen deprivation therapy as compared to benign tissue, and further increased in patients with CRPC. Taken together this study therefore demonstrates that the ratio of AKR1C3:17βHSD2 is more important than AKR1C3 expression alone in determining intratumoral androgen levels and that 11-oxygenated androgens may play a bigger role in CRPC than previously anticipated.

Authors: Monique Barnard, Jonathan L. Quanson, Elahe Mostaghel, Elzette Pretorius, Jacky L. Snoep, Karl-Heinz Storbeck

Date Published: 1st Oct 2018

Publication Type: Not specified

Targeting glycolysis in the malaria parasite Plasmodium falciparum

Abstract (Expand)

Glycolysis is the main pathway for ATP production in the malaria parasite Plasmodium falciparum and essential for its survival. Following a sensitivity analysis of a detailed kinetic model for glycolysis … in the parasite, the glucose transport reaction was identified as the step whose activity needed to be inhibited to the least extent to result in a 50% reduction in glycolytic flux. In a subsequent inhibitor titration with cytochalasin B, we confirmed the model analysis experimentally and measured a flux control coefficient of 0.3 for the glucose transporter. In addition to the glucose transporter, the glucokinase and phosphofructokinase had high flux control coefficients, while for the ATPase a small negative flux control coefficient was predicted. In a broader comparative analysis of glycolytic models, we identified a weakness in the P. falciparum pathway design with respect to stability towards perturbations in the ATP demand.

Authors: David D. van Niekerk, Gerald P. Penkler, Francois du Toit, Jacky L. Snoep

Date Published: 1st Feb 2016

Publication Type: Not specified

Quantitative analysis of drug effects at the whole-body level: a case study for glucose metabolism in malaria patients

Abstract (Expand)

We propose a hierarchical modelling approach to construct models for disease states at the whole-body level. Such models can simulate effects of drug-induced inhibition of reaction steps on the whole-body … physiology. We illustrate the approach for glucose metabolism in malaria patients, by merging two detailed kinetic models for glucose metabolism in the parasite Plasmodium falciparum and the human red blood cell with a coarse-grained model for whole-body glucose metabolism. In addition we use a genome-scale metabolic model for the parasite to predict amino acid production profiles by the malaria parasite that can be used as a complex biomarker.

Authors: J. L. Snoep, K. Green, J. Eicher, D. C. Palm, G. Penkler, F. du Toit, N. Walters, R. Burger, H. V. Westerhoff, D. D. van Niekerk

Date Published: 27th Nov 2015

Publication Type: Not specified

Entrainment of heterogeneous glycolytic oscillations in single cells

Abstract (Expand)

Cell signaling, gene expression, and metabolism are affected by cell-cell heterogeneity and random changes in the environment. The effects of such fluctuations on cell signaling and gene expression … have recently been studied intensively using single-cell experiments. In metabolism heterogeneity may be particularly important because it may affect synchronisation of metabolic oscillations, an important example of cell-cell communication. This synchronisation is notoriously difficult to describe theoretically as the example of glycolytic oscillations shows: neither is the mechanism of glycolytic synchronisation understood nor the role of cell-cell heterogeneity. To pin down the mechanism and to assess its robustness and universality we have experimentally investigated the entrainment of glycolytic oscillations in individual yeast cells by periodic external perturbations. We find that oscillatory cells synchronise through phase shifts and that the mechanism is insensitive to cell heterogeneity (robustness) and similar for different types of external perturbations (universality).

Authors: Anna-Karin Gustavsson, Caroline B. Adiels, Bernhard Mehlig, Mattias Goksör

Date Published: 1st Aug 2015

Publication Type: Not specified

Construction and validation of a detailed kinetic model of glycolysis in Plasmodium falciparum

Abstract (Expand)

The enzymes in the Embden–Meyerhof–Parnas pathway of Plasmodium falciparum trophozoites were kinetically characterized and their integrated activities analyzed in a mathematical model. For validation … of the model, we compared model predictions for steady-state fluxes and metabolite concentrations of the hexose phosphates with experimental values for intact parasites. The model, which is completely based on kinetic parameters that were measured for the individual enzymes, gives an accurate prediction of the steady-state fluxes and intermediate concentrations. This is the first detailed kinetic model for glucose metabolism in P. falciparum, one of the most prolific malaria-causing protozoa, and the high predictive power of the model makes it a strong tool for future drug target identification studies. The modelling workflow is transparent and reproducible, and completely documented in the SEEK platform, where all experimental data and model files are available for download.

Authors: Gerald Penkler, Francois du Toit, Waldo Adams, Marina Rautenbach, Daniel C. Palm, David D. van Niekerk, Jacky L. Snoep

Date Published: 1st Apr 2015

Publication Type: Not specified

Allosteric regulation of phosphofructokinase controls the emergence of glycolytic oscillations in isolated yeast cells

Abstract

Not specified

Authors: Anna-Karin Gustavsson, David D. van Niekerk, Caroline B. Adiels, Bob Kooi, Mattias Goksör, Jacky L. Snoep

Date Published: 1st Jun 2014

Publication Type: Not specified

Heterogeneity of glycolytic oscillatory behaviour in individual yeast cells

Abstract

Not specified

Authors: Anna-Karin Gustavsson, David D. van Niekerk, Caroline B. Adiels, Mattias Goksör, Jacky L. Snoep

Date Published: 3rd Jan 2014

Publication Type: Not specified

Sustained glycolytic oscillations in individual isolated yeast cells

Abstract

Not specified

Authors: Anna-Karin Gustavsson, David D. van Niekerk, Caroline B. Adiels, Franco B. du Preez, Mattias Goksör, Jacky L. Snoep

Date Published: 1st Aug 2012

Publication Type: Not specified

From steady-state to synchronized yeast glycolytic oscillations II: model validation.

Abstract (Expand)

UNLABELLED: In an accompanying paper [du Preez et al., (2012) FEBS J279, 2810-2822], we adapt an existing kinetic model for steady-state yeast glycolysis to simulate limit-cycle oscillations. Here we … validate the model by testing its capacity to simulate a wide range of experiments on dynamics of yeast glycolysis. In addition to its description of the oscillations of glycolytic intermediates in intact cells and the rapid synchronization observed when mixing out-of-phase oscillatory cell populations (see accompanying paper), the model was able to predict the Hopf bifurcation diagram with glucose as the bifurcation parameter (and one of the bifurcation points with cyanide as the bifurcation parameter), the glucose- and acetaldehyde-driven forced oscillations, glucose and acetaldehyde quenching, and cell-free extract oscillations (including complex oscillations and mixed-mode oscillations). Thus, the model was compliant, at least qualitatively, with the majority of available experimental data for glycolytic oscillations in yeast. To our knowledge, this is the first time that a model for yeast glycolysis has been tested against such a wide variety of independent data sets. DATABASE: The mathematical models described here have been submitted to the JWS Online Cellular Systems Modelling Database and can be accessed at http://jjj.biochem.sun.ac.za/database/dupreez/index.html.

Authors: F. B. du Preez, D. D. van Niekerk, J. L. Snoep

Date Published: No date defined

Publication Type: Not specified

From steady-state to synchronized yeast glycolytic oscillations I: model construction.

Abstract (Expand)

UNLABELLED: An existing detailed kinetic model for the steady-state behavior of yeast glycolysis was tested for its ability to simulate dynamic behavior. Using a small subset of experimental data, the … original model was adapted by adjusting its parameter values in three optimization steps. Only small adaptations to the original model were required for realistic simulation of experimental data for limit-cycle oscillations. The greatest changes were required for parameter values for the phosphofructokinase reaction. The importance of ATP for the oscillatory mechanism and NAD(H) for inter-and intra-cellular communications and synchronization was evident in the optimization steps and simulation experiments. In an accompanying paper [du Preez F et al. (2012) FEBS J279, 2823-2836], we validate the model for a wide variety of experiments on oscillatory yeast cells. The results are important for re-use of detailed kinetic models in modular modeling approaches and for approaches such as that used in the Silicon Cell initiative. DATABASE: The mathematical models described here have been submitted to the JWS Online Cellular Systems Modelling Database and can be accessed at http://jjj.biochem.sun.ac.za/database/dupreez/index.html.

Authors: F. B. du Preez, D. D. van Niekerk, B. Kooi, J. M. Rohwer, J. L. Snoep

Date Published: No date defined

Publication Type: Not specified

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