Limonene Synthase

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Reaction catalysed

Failed to parse (Cannot store math image on filesystem.):  \begin{align}   Geranyl diphosphate  {\begin{smallmatrix}\displaystyle\longrightarrow \\ \displaystyle\longleftarrow \end{smallmatrix}}  Limonene + Diphosphate \end{align}

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
Geranyldiphosphate	GPP	C10H20O7P2	314.209	17211	41432	445995
Limonene	Limonene	C10H16	136.24	15384	449062	22311 or 439250
Diphosphate	PP	O7P2	173.94			644102

Equation Rate

Failed to parse (Cannot store math image on filesystem.): V_\mathrm{LimSynth} = Vmax_\mathrm{forward} * \cfrac {\cfrac{[GPP]}{Km_\mathrm{GPP}} * \left ( 1 - \cfrac {[Limonene]*[PP]}{[GPP]*K_\mathrm{eq}} \right )}{\left (1 + \cfrac {[GPP]}{Km_\mathrm{GPP}} + \cfrac {[Limonene]}{Km_\mathrm{Limonene}} \right) * \left (1 + \cfrac {[PP]}{Km_\mathrm{PP}} \right)}

Parameter	Description	Reference
VLimSynth	Reaction rate for Limonene Synthase	ref
Vmaxforward	Maximum reaction rate towards the production of limonene	ref
KmGPP	Michaelis-Menten constant for GPP	ref
KmLimonene	Michaelis-Menten constant for Limonene	ref
KmPP	Michaelis-Menten constant for PP	ref
Keq	Equilibrium constant	ref
[GPP]	GPP concentration	ref
[Limonene]	Limonene concentration	ref
[PP]	PP concentration	ref

Strategies for estimating the kinetic parameter values

Calculating the Equilibrium Constant

The equlibrium constant, K_eq, can be calculated from the Gibbs free energy of a reaction, ΔG_r, using the Van't Hoff isotherm equation:

$K_\mathrm{eq} = exp \left ( \cfrac {-ΔG^{°'}}{RT} \right )$

where:

This column is 100 points wide	This column is 200 points wide
Keq	Equilibrium constant
-ΔG°	Gibbs free energy change
R	Gas constant with a value of 8.31 JK-1mol-1
T	Temperature which is always expressed in kelvin

Extracting Information from Limonene Production Rates

Amount produced (mg/L)	Time (H)	Organism	Description	Reaction Flux (µM/s)
5	24	Escherichia coli	Possible reason for the low limonene production might due to the insufficient supply of IPP and DMAPP .	0.0255
335	48	Escherichia coli	Engineered E.coli in which heterologous MVA pathway was installed .	0.8537
35.8	48	Escherichia coli	E.coli was engineered to express GPPS, LS, DXS, and IDI .	0.0912
4.87	48	Escherichia coli	This was the initial titer. The study established a limonene biosynthesis pathway in E.coli using four different polycistronic operons based on 3 vectors with varied expression strength .	0.0124
17.4	48	Escherichia coli	Using a plasmid with DXS and IDI over expressed .	0.0445
430	72	Escherichia coli		0.7306

Published Kinetic Parameter Values

Km (mM)	Vmax	Kcat (s-1)	Kcat/Km	Organism	Description
0.00125	-	-	-	Ricciocarpos natans	GPP -> Limonene
0.0018	-	-	-	Mentha piperita	GPP -> Limonene
0.00625	0.08 µmol/min/mg	0.08	1.5	Cannabis sativa L.	GPP -> Limonene
0.00496	0.13 µmol/min/mg	0.14	2.9	Cannabis sativa L.	GPP -> Limonene
0.0031	28.49 µmol/h/mg	-	-	Citrus limon	GPP -> Limonene
0.016	-	0.02	-	Escherichia coli	GPP -> Limonene
0.0068	-	0.082	-	Cannabis sativa L.	GPP -> Limonene
0.0067	-	0.081	-	Cannabis sativa L.	GPP -> Limonene