Glucose Transporter

Glucose transporters are a wide group of membrane proteins that facilitate the transport of glucose over a plasma membrane. Glucose is a vital source of energy for all life.

Chemical equation

$Glucose_{out} \rightleftharpoons Glucose_{in}$

Rate equation

Mono-Substrate reversible Michaelis-Menten with Haldane substitution is used.

$v = \frac{V_{mf}\Big([Glucose_{out}] - \frac{[Glucose_{in}]}{K_{eq}}\Big)}{K_{Glucose_{out}}\Big(1 + \frac{[Glucose_{in}]}{K_{Glucose_{in}}}\Big) + [Glucose_{out}]}$

Parameter values

Parameter	Value	Units	Organism	Remarks
$V_{mf}$	.017	$\text{mM min}^{-1}$	HeLa cell line	Vm is converted to $\text{mM min}^{-1}$ from U × (mg total cellular protein) at $37^{\circ}$C
$K_{eq}$	1
$K_{Glucose_{in}}$	9.3	mM
$K_{Glucose_{out}}$	10	mM

Parameters with uncertainty

Thirteen isoforms of Glucose transporter (GLUT) exist in Mammalian cells to facilitate the uptake of glucose from extracellular fluid into the cell. However, in most of the literature the kinetic properties of GLUT 1-4 isoforms are only reported . In our model $K_{m}$ value for the forward reaction is taken from the paper Modeling cancer glycolysis. The mean and std. dev. of $K_{m}$ for the reverse reaction is being averaged from the 4 isoforms of GLUT reported in Zhao et. al..

Parameter	Value	Units	Organism	Remarks
$V_{mf}$	$0.0172\pm 0.0064$	$\text{mM min}^{-1}$	HeLa cell line
$K_{eq}$	$K_{eq}$ value is sampled based on the Haldane relation $K_{eq} = \frac{V_{forward}*K_{product}}{V_{reverse}*K_{substrate}}$ Alternative: The $K_{eq}$ value of the transporters are reported to be 1.00. As the $K_{eq}$ is directly related to $K_{m}$ values of substrate and product, the uncertainty would also be dependent. The highest uncertainty is mentioned for $K_{Glucose_{out}}$ which is $70%$ of the actual value. The same percentage of error is assumed for $K_{eq}$; $0.70$
$K_{Glucose_{in}}$	$9.3 \pm 3.3$	mM	Multiple sites of human cell as 4 isoforms were considered
$K_{Glucose_{out}}$	$8.0 \pm 5.64$	mM