Nickotine

I come from a chemistry background and so I’m used to thinking in terms of proportions, so forgive me if my thinking is completely wrong. *** I’d like to simulate a reaction that occurs in the human body. I will keep the pH and temperature the same as it is in the human body so the enzyme can function optimally, it is a lactonase enzyme found in human blood so I think these 2 factors wil be important. From what I understand enzymes can become saturated and won’t work once they reach this point so there is some logic behind my thinking. Therefore there must be an ideal or threshold amount of the enzyme to use. *** Generally how is this calculated? Is it per mol? Or is it specific for each enzyme and the task it performs? I am struggling to find any information about this on the web and so would appreciate some insight into this problem.