Reader Nico has an interesting question on the subject of enzymes: do they ever quit? Which is to say, do they stop working at some point just naturally, run out of go-juice or something along those lines? Nico, I’m not an organic chemist but when’t the last time I let that stop me? I believe the answer is no. Enzymes are not living organisms, so as far as I know they don’t run out of energy or anything like that. They are organic molecules (proteins) that living organisms use to perform very specific chemical jobs, converting x molecule — but only x molecule — into molecules y and z if that makes sense.
I think of them as sort of free-floating puzzle pieces. They lock onto a specific molecule, break it, move on to the next molecule, break it and so on, over and over and over again until they either run out of “x” molecules to break or are themselves damaged. A great illustration of this principle can be observed with a starch-thickened custards like pastry cream. Human saliva abounds in a starch-busting (amylose-busting) enzyme called amylase. When that busting occurs on a large enough scale the gel that gives pastry cream its thick texture breaks down, and fast. Which is why pastry cream liquifies so quickly in the mouth. It’s also why, if you introduce some amylase into a quantity of pastry cream by say, double dipping with a spoon, you run the risk of turning the entire batch into a runny mess. Very interesting things, those enzymes. Thanks for the question, Nico!