Metabolic Control Analysis: A Tool for Designing Strategies to Manipulate Metabolic Pathways

Table 4

Control of GSH and PC synthesis in plants exposed to Cd²⁺.

Enzyme	1x γ-ECS + PCS				2.5x γ-ECS + PCS
	𝐶^𝐽GSH𝑣𝑖	𝐶^𝐽PC𝑣𝑖	𝐶^GSH𝑣𝑖	𝐶^PC𝑣𝑖	𝐶^𝐽GSH𝑣𝑖	𝐶^𝐽PC𝑣𝑖	𝐶^GSH𝑣𝑖	𝐶^PC𝑣𝑖
γ-ECS	0.58	0.60	0.68	0.76	0.45	0.61	0.70	0.60
GS	<0.01	<0.01	0.01	0.01	0.19	<0.01	<0.01	0.97
GS-transferase	0.01	−0.06	−0.07	−0.07	<0.01	<0.01	<−0.01	−0.05
PCS	0.40	0.44	−0.63	−0.56	0.33	0.44	−0.62	0.57
vacuole PC-Cd transporter	<0.01	<0.01	<0.01	−1.2	<0.01	<0.01	<0.01	−2.1

𝐶^𝐽GSH_𝑣𝑖, control coefficient of enzyme 𝑖 in GSH synthesis; 𝐶^𝐽PC_𝑣𝑖, control coefficient of enzyme Ei on PCs synthesis; 𝐶^GSH_𝑣𝑖, control coefficient of enzyme 𝑖 on GSH concentration; 𝐶^PC_𝑣𝑖, control coefficient of enzyme 𝑖 on PCs concentration. An enzyme with a negative flux control indicates that it is localized in a branch, turning aside the principal flux; an enzyme with a negative concentration control indicates that an increase in its activity decreases metabolite concentration.