Limonene-6-Hydroxylase (L6H)

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What we know

This enzyme is also known as (S)-limonene 6-monooxygenase, (-)-limonene 6-hydroxylase, (-)-limonene 6-monooxygenase, (-)-limonene,NADPH:oxygen oxidoreductase (6-hydroxylating)

Reaction catalysed

$Limonene + NADPH + O_2 \rightleftharpoons (-)-trans-isopiperitenol + NADP^+ + H_2O$

Metabolite and Enzyme Background Information

Long metabolite and enzyme names are abbreviated in the model for clarity and standard identification purposes.

Metabolite	Abbreviation	Chemical Formula	Molar mass (g/mol)	ChEBI	ChEMBL	PubChem	MetaCyc
(-)-4S-limonene	Limonene	C10H16	136.24	15384	449062	22311 or 439250
(-)-trans-carveol	carveol	Chemical Formula	Molar mass (g/mol)	ChEBI	ChEMBL	PubChem	MetaCyc
NADPH	NADPH	Chemical Formula	Molar mass (g/mol)	ChEBI	ChEMBL	PubChem	MetaCyc
NADP	NADP	Chemical Formula	Molar mass (g/mol)	ChEBI	ChEMBL	PubChem	MetaCyc
Limonene-6-hydroxylase	L6H	Chemical Formula	Molar mass (g/mol)	ChEBI	ChEMBL	PubChem	LIMONENE-6-MONOOXYGENASE-RXN
Metabolite	Abbreviation	Chemical Formula	Molar mass (g/mol)	ChEBI	ChEMBL	PubChem	MetaCyc

Equation Rate

$V_\mathrm{LimSynth} = Vmax_\mathrm{forward} * \cfrac {\cfrac{[GPP]}{Km_\mathrm{GPP}} * \left ( 1 - \cfrac {[Limonene]*[PP]}{[GPP]*K_\mathrm{eq}} \right )}{1 + \cfrac {[GPP]}{Km_\mathrm{GPP}} + \cfrac {[Limonene]}{Km_\mathrm{Limonene}} + \cfrac {[PP]}{Km_\mathrm{PP}} + \cfrac {[Limonene]*[PP]}{Km_\mathrm{Limonene}*Km_\mathrm{PP}}}$

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 equilibrium constant can be calculated using the Van't Hoff Isotherm equation:

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

$= exp \left ( \cfrac {-(XY \text { kJmol}^{-1})}{ (8.31 \text{ JK}^{-1} \text { mol}^{-1} * 289 K} \right )$

$= exp \left ( \cfrac { XY \text { kJmol}^{-1} }{ 2401.59 \text{ JK}^{-1}\text { mol}^{-1} }\right)$

$= exp \left ( \cfrac{ XY \text { Jmol}^{-1}}{2401.59 \text{ JK}^{-1}\text { mol}^{-1}} \right)$

$=exp \left ( XY \right )$

$= (INSERT RESULT)$

where;

Keq	Equilibrium constant
-?G°	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

Standard Gibbs Free energy

No information yet could be found on the standard Gibbs free energy for L6H. However, Metacyc has the standard Gibbs free energy value for Limonene oxide, catalysing the formation of cis-carveol from limonene [RXN-9465] as -92.52051 kcal·mol^-1 .

Published Kinetic Parameter Values

Km Values

Km (mM)	Unit	Substrate / Product	Directionality	Organism	References
Value	unit	substrate	directionality	organism	Ref

μ :-5.05354 , σ : 0.49474

Vmax values

Vmax	Unit	Directionality	Organism	References
Value	µmol/min/mg (unit)	directionality	Organism	References

Kcat values

Kcat	Unit	Organism	Reference
value	s-1	Organism	ref e.g. Alonso 1992

Extracting Information from (INSERT SUBSTRATE/PRODUCT) Production Rates

Amount produced (mg/L)	Time (H)	Organism	Description	Reaction Flux (µM/s)
X	X	Y	Z	Z
X	X	Y	Z	Z
X	X	Y	Z	Z
X	X	Y	Z	Z
X	X	Y	Z	Z
X	X	Y	Z	Z

Published Kinetic Parameter Values

Km (mM)	Vmax	Kcat (s-1)	Kcat/Km	Organism	Description
0.00125	-		-	Z	A -> B
0.0018	-	-	-	Z	A -> B
Y	Y	Y	Y	Z	A -> B
Y	Y	Y	Y	Z	A -> B
Y	Y	-	-	Z	A -> B
Y	-	Y	-	Z	GPP -> B
Y	-	Y	-	Z	GPP -> B
x	-	y	-	Z.	A -> B

Detailed descriptions of kinetic values used in this model

A more detailed description of the kinetic values listed above can be found here.