TABLE 9

Induction, inhibition or catalytic change in enzyme activity

Induction is related to the metabolic activity (increase in free enzyme E or catalytic activity k_cat) which means an increase in synthesis k_syn or decrease in loss k_deg, or increase in k_cat. Inhibition involves the opposite.

Observation	Cause	V_max	K_m	Cl(S)	Commentary
Induction	k_syn ↑	↑	↔	↑	If k_syn increases free enzyme E concentration increases. K_m is unaffected. Substrate clearance increases (von Bahr et al., 1998)
	k_deg ↓	↑	↔	↑	If k_deg decreases free enzyme E concentration increases. K_m is unaffected. Substrate clearance increases (Ethanol induction of CYP2E1 in (Hu et al., 1995)
Inhibition	k_syn ↓	↓	↔	↓	If k_syn decreases free enzyme E concentration decreases. K_m is unaffected (Ramsay and Tipton, 2017)
	k_deg ↑	↓	↔	↓	If k_deg increases free enzyme E concentration decreases. K_m is unaffected (Ramsay and Tipton, 2017)
Catalytic change	k_cat ↑	↑	↑	↔ (↑)	If k_cat increases V_max increases. K_m increases if k_cat ≈ k_off. Substrate clearance is unaffected if V_max and K_m changes the same.
	k_cat ↓	↓	↓	↔ (↓)	If k_cat decreases V_max decreases. K_m decreases if k_cat ≈ k_off. Substrate clearance is unaffected if V_max and K_m changes the same.