Phosphofructokinase type 1

The enzyme Phosphofructokinase Type-1 uses another ATP molecule to transfer a phosphate group to Fru6P to form fructose 1, 6-bisphosphate. PFK-1 is an allosteric enzyme showing cooperative behaviour with Fru6P and hyperbolic kinetics with ATP.

Chemical equation

$Fru6P + ATP \rightleftharpoons Fru1,6BP + ADP$

Rate equation

The concerted transition model of Monod, Wyman and Changeux (MWC model) is used as a rate equation for this tetrameric enzyme for considering exclusive ligand binding (F6P, activators and inhibitors) together with mixed type activation, (Fru2,6BP or AMP or Pi) .

Failed to parse (Cannot store math image on filesystem.): v = Vm\left (\left (\frac{\frac{[ATP]}{Km_{ATP}}}{1 + \frac{[ATP]}{Km_{ATP}} }\right ) \left ( \frac{ 1 + \frac{[\beta Fru2,6BP]}{ \alpha Ka_{Fru2,6BP} } }{ 1 + \frac{[Fru2,6BP]}{ \alpha Ka_{Fru2,6BP} } } \right ) \left( \frac{\frac{[Fru6P]\left(1+\frac{[Fru2,6BP]}{[\alpha Ka_{Fru2,6BP}]}\right)}{Km_{Fru6P}\left(1 + \frac{[Fru2,6BP]}{Ka_{Fru2,6BP}}\right)} \left[1 + \frac{[Fru6P]\left(1+\frac{[Fru2,6BP]}{\alpha Ka_{Fru2,6BP}}\right)}{Km_{Fru6P}\left(1 + \frac{[Fru2,6BP]}{Ka_{Fru2,6BP}}\right)} \right]^3} { \frac{L\left( 1 + \frac{[CIT]}{Ki_{CIT}}\right)^4\left(1 + \frac{[ATP]}{Ki_{ATP}}\right)^4}{\left(1+\frac{[Fru2,6BP]}{Ka_{Fru2,6BP}}\right)^4} + \left[1 + \frac{Fru6P\left(1+\frac{Fru2,6BP}{\alpha Ka_{Fru2,6BP}}\right)}{Km_{Fru6P}\left(1 + \frac{[Fru2,6BP]}{Ka_{Fru2,6BP}}\right)} \right]^4 } - \left( \frac{\frac{[ADP][Fru1,6BP]}{K_{ADP}K_{Fru1,6BP}K_{eq}}}{\frac{[ADP]}{K_{ADP}} + \frac{[Fru1,6BP]}{K_{Fru1,6BP}} + \frac{[ADP][Fru1,6BP]}{K_{ADP}K_{Fru1,6BP}} + 1 } \right) \right) \right)

Parameter values

Parameter	Value	Units	Organism	Remarks
$Vm_{r}$	0.031	$mM \times min^{-1}$	HeLa cell line	Moreno-Sánchez, Marín-Hernández, Encalada & Saavedra, unpublished results
$Km_{Fru6P}$	1.0	mM
$Km_{ATP}$	0.021	mM
$Ki_{ATP}$	20	mM
$Ki_{CIT}$	6.8	mM
$Ka_{Fru2,6BP}$	$8.4 \times 10^{-4}$	mM
$\alpha$	0.32	Dimensionless
$\beta$	0.98	Dimensionless
$L$	4.1	Dimensionless
$K_{ADP}$	5	mM
$K_{Fru1,6BP}$	5	mM
$K_{eq}$	247	mM		Recalculated from the $ΔGº´ = - 31.4 KJ mol^{-1}$

Parameters with uncertainty

• The $\alpha$ and $\beta$ in the rate equation represents the factors by which the ligand affinity and catalytic capacity are modified in the presence of an allosteric activatory . As $Fru2,6BP$ is the only activator in our model we considered the $\alpha$ and $\beta$ value of $Fru2,6BP$, $\alpha_{Fru2,6BP} = 0.75\pm 0.4$ and $\beta_{Fru2,6BP} = 1.18\pm 0.17$. These two values are measured in the presence of 140 $\text{mM K}^{+}$ medium .

• The Vm value is reported as Failed to parse (Cannot store math image on filesystem.): 56 \pm 23 (nmol/min/mg protein). HeLa cells were harvested at a concentration of 65 mg protein/ml . Converting Vm to mM/min becomes Failed to parse (Cannot store math image on filesystem.): 0.00364 \pm 0.001495 again in the presence of 140 $\text{mM K}^{+}$.

Parameter	Value	Units
$Vm_{r}$	Failed to parse (Cannot store math image on filesystem.): 0.00364 \pm 0.001495	$mM \times min^{-1}$
$Km_{Fru6P}$	$1.1 \pm 0.4$	mM
$Km_{ATP}$	0.021	mM
$Ki_{ATP}$	20	mM
$Ki_{CIT}$	$6.7 \pm 3.8$	mM
$Ka_{Fru2,6BP}$	$0.00099 \pm 0.00014$	mM
$\alpha$	0.32	Dimensionless
$\beta$	0.98	Dimensionless
$L$	4.1	Dimensionless
$K_{ADP}$	5	mM
$K_{Fru1,6BP}$	5	mM
$K_{eq}$	247	mM