Table 1.

Different trends in the temperature dependences of k_cat and k_cat/K_m for WT and Y68A COMT, highlighting the breakpoint in E_a with temperature with Y68A

COMT	kcat, s−1			kcat/Km, M−1, s−1
	Ea(bb)	Ea(ab)	ΔEa (Ea(bb)-Ea(ab))	Ea(bb)	Ea(ab)	ΔEa (Ea(bb)-Ea(ab))
WT	← 13.1(0.5) →			← 18.8(0.5)→
Y68A	27.3( 0.6)	18.0(0.9)	9.3(1.4)	28.7(0.5)	20.7(0.8)	7.9(1.3)
ΔEa(Y68A-WT)	14.2(1.1)	4.9(1.4)		9.8(0.8)	1.9(1.3)

The E_a and ΔE_a values are all kcal/mol. E_a(ab), activation energies above the breakpoint; E_a(bb), activation energies below the breakpoint.