# gnuplot script to simulate the pH depent activity of an ionizable enzyme
# Foster 5/10/06
# 
# Functions: 
        v(x) = s*Vpm(x)/(s+Kpm(x))
        f1(x)= 10**-x/10**-pKe1 + 1 + 10**-pKe2/10**-x
        f2(x)= 10**-x/10**-pKes1 + 1 + 10**-pKes2/10**-x
        Vpm(x) = Vm/f2(x)
        Kpm(x) = Km*f1(x)/f2(x)

# Variables:
        Vm = 1
        Km = 1e-6
        pKe1 = 3
        pKe2 = 9
        pKes1 = 3
        pKes2 = 9
        s = 10e-6

# Title, Labels
set title "Effect of Enzyme Ionization on Steady-State Kinetics"
set xlabel 'pH'
set ylabel 'v0'
set label 1 "Vmax = %3.2f ", Vm at graph 0.7, 0.95
set label 2 "Km = %3.2e ", Km at graph 0.7, 0.9
set label 3 "[S] = %3.2e ", s at graph 0.7, 0.85
set label 4 "pKe1 = %3.2f ", pKe1 at graph 0.7, 0.8
set label 5 "pKes1 = %3.2f", pKes1 at graph 0.7, 0.75
set label 6 "pKe2 = %3.2f ", pKe2 at graph 0.7, 0.7
set label 7 "pKes2 = %3.2f", pKes2 at graph 0.7, 0.65

# plot it
	plot [0:14] v(x) lw 3 notitle