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Mar 18, 2021
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.
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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.
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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.
Relevant answer
Mar 19, 2021
Answer
You have a misconception, which I totally understand due to your background. When the enzymes become "saturated" it doesn't mean they "don't work". They will keep working, the reactions will still occur, it's just that the speed of the reaction won't increase any further even if you add more substrate.
Enzymes are not consumed in reactions. They're like workers in a factory, they process the material (substrate) into product, but they themselves are not consumed to become product. So the amount of workers will remain the same over time.
Now, if you have a lot of workers and little material, many of them will just lazy around doing nothing. In this situation, if you add more material, those free workers will get to work, and you produce the product faster.
But, if you keep adding material faster, at some point all the workers will be busy. At that point, even if you pile another mountain of material at the gate every minute, the speed that you produce the product will not increase any further. We refer to this situation as the enzyme is "saturated". Make no mistake, even when it's "saturated", the production is still occurring. And if you stop adding material (substrate), the backlog of substrate you have already added will slowly be processed by the enzyme until all of it becomes product.
So in the end, you'll get your reaction and your product no matter how much enzyme you add. Even if it's just 1 molecule of enzyme, it will get the job done, eventually. The only difference is time, i.e. how long you have to wait until that amount of substrate you added turns into product. We usually refer to this speed as "enzyme unit", or U. 1 U of an enzyme means that if all those enzyme molecules get to work (equivalent to enzyme saturation), they will convert 1 micromole of substrate per minute to product.
So the amount of enzyme you need to use all comes down to how long you prefer to wait. If, for example, you have 300 micromoles of substrate, and you only want to wait 20 minutes for the reaction to end, you will need to add:
Amount of enzyme = 300/20 = 15 (U)
Please understand that this is just a grossly simplified explanation of the most basic. When you get to the actual enzyme speed, there are a bunch of other factors you need to mind, such as the chance of collision between enzyme and substrate molecules (which depends on temperature and dilution, similar to normal chemical reaction), the nature of the enzyme (which determines how stickily it catch the substrate molecule when they collide or whether they'll just bounce off each other, how stickily the product bounds to the enzyme and delays further substrate coming in, whether the enzyme needs to change its structure and therefore requires a recovery time, etc.), how many substrates take part in the reaction, the presence of inhibitor/inducer, etc. It can get complicated super fast and there's a whole field of study for it. If you're interested in it, you can start by learning about Michaelis–Menten kinetics, which is the most fundamental of them all.