function [ dXdt ] = nataliewilliamsDE(t,X)
% this function defines the enzymatic differential equation
global V K

dXdt = zeros(size(X));

s = X(1); %substrate

dsdt = -V*s/(K+s);
dpdt = V*s/(K+s);

dXdt(1) = dsdt;
dXdt(2) = dpdt;
end