Menthone:Menthol reductase (MMR)
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Contents
What we know
Menthone: menthol reductase(s) (MMR) catalyses the NADPH-dependent convertion of menthone to menthol and the conversion of isomenthone to isomenthol.
Issues
Strategies
Reaction catalysed
Enzyme and Metabolite Background Information
Long metabolite names are abbreviated in the model for clarity and standard identification purposes.
Metabolite | Abbreviation | Chemical Formula | Molar mass (g/mol) | ChEBI | ChEMBL | PubChem | BRENDA | PlantCyc |
---|---|---|---|---|---|---|---|---|
menthone:menthol reductase | MMR | 34070 Da [1], 35000 Da [2] | 1.1.1.207 | |||||
menthone | ||||||||
isomenthone | ||||||||
NADPH | C21H30N7O17P3 | 745.42116 | 16474 | |||||
NADP+ | C21H29N7O17P3 | 744.41322 | 18009 |
Equation Rate
Two MMR reactions are included in the kinetic model with one converting menthone to menthol and isomenthone, and one converting isomenthone to isomenthol. Both reactions are parameterised using random Bi-Bi reversible Michaelis-Menten equation.
Reaction 1: Conversion of menthone to menthol
Reaction 2: Conversion of isomenthone to isomenthol
Parameter | Description | Units |
---|---|---|
VMMR | Reaction rate for MMR | μM/min |
Kcatforward | Catalytic constant in the forward direction | s-1 |
Kmmenthone | Michaelis-Menten constant for menthone | μM |
Kmmenthol | Michaelis-Menten constant for menthol | μM |
Kmisomenthone | Michaelis-Menten constant for isomenthone | μM |
Kmisomenthol | Michaelis-Menten constant for isomenthol | μM |
KmNADPH | Michaelis-Menten constant for NADPH | μM |
KmNADP | Michaelis-Menten constant for NADP+ | μM |
Keq | Equilibrium constant | |
[MMR] | enzyme concentration | μM |
[menthol] | menthol concentration | μM |
[menthone] | Menthone concentration | μM |
[isomenthone] | Isomenthone concentration | μM |
[isomenthol] | Isomenthol concentration | μM |
[NADPH] | NADPH concentration | μM |
[NADP] | NADP+ concentration | μM |
Strategies for estimating the kinetic parameter values
Standard Gibbs Free energy
The Gibbs free energy for PGR is -3.9565125 kcal.mol^-1. This value is estimated from the 'Contribution group' method by Latendresse, M. and is available from MetaCyc (EC 1.3.1.81) [3].
Calculating the Equilibrium Constant
The equilibrium constant can be calculated using the Van't Hoff Isotherm equation:
where;
Keq | Equilibrium constant |
-ΔG° | Gibbs free energy change. For (INSERT ENZYME) it is (INSERT VALUE) kJmol-1 |
R | Gas constant with a value of 8.31 JK-1mol-1 |
T | Temperature which is always expressed in kelvin |
Extracting Information from menthone Production Rates
A table will go here
Published Kinetic Parameter Values
Km Values
Parameter | Directionality | Substrate / Product | Value | unit | Method notes | References |
---|
Parameter uncertainty
Probability distribution has been generated for each of the parameter in this reaction.
Parameter | Direction | Substrate | Value | Unit | Weight | weight counter |
Km | Forward | isomenthone | 35 | µM | 512 | 512 |
Km | Forward | isomenthone | 41 | µM | 512 | 1024 |
Km | Forward | isomenthone | 46 | µM | 512 | 1536 |
Km | Forward | isomenthone | 81 | µM | 512 | 2048 |
Km | Forward | isomenthone | 86.4 | µM | 512 | 2560 |
Km | Forward | isomenthone | 91.8 | µM | 512 | 3072 |
Detailed description of kinetic values obtained from literature
A more detailed description of the values listed above can be found here .
Simulations
References
- ↑ Davis, E.M. et. al. (2005). "Monoterpene metabolism. Cloning, Expression, and Characterization of Menthone Reductases from Peppermint.", Vol 137, pp. 873-881
- ↑ Kjonaas, R. et. al. (1982). Metabolism of monoterpenes: Conversion of l-Menthone to l-Menthol and d-Neomenthol by stereospecific dehydrogenases from peppermint (Mentha piperita) leaves, vol 69, pp.1013-1017.
- ↑ Latendresse M. (2013). "Computing Gibbs Free Energy of Compounds and Reactions in MetaCyc."