global k1 km1 k2 e0

x0 = [1;0.1;0;0];

t = 0:0.1:100;

k1 = 1;
km1 = 1;
k2 = 5;

K = (km1+k2)/k1;

e0 = x0(2);

[tt,xx] = ode45('catalysis',t,x0);

y0 = x0(1);

[ts,ys] = ode45('michaelis_menten',t,y0);
cs      = e0*ys./(ys+K);
figure
plot(tt,xx),legend('susbtrate','enzyme','complex','product');

figure
plot(tt,[xx(:,1),xx(:,3),ys,cs]),legend('susbtrate','complex','MM substrate','MM complex');