Hey, everyone. So let's take a look at the following example question. Here it says provide the mechanism for the enzyme catalyzed reaction between ATP and a nucleophile. Now remember, we have our 4 steps. Step 0 is kind of just the prep phase where we have to reduce the overall negative charge of our ATP molecule so that a nucleophile can then go in and attack the phosphorus atom.

So step 0 is our ionic bond formation, which is talking about the magnesium complex that will be formed. Step 1 would then be nucleophilic attack, step 2 would be proton transfer, and then finally step 3 would be our loss of leaving group. So for step 0, we're going to say here that our magnesium ion forms an ionic bond with 2 of the negatively charged oxygens of the phosphate anhydride. So here goes our ATP molecule, we have our magnesium with its class of enzymes, so we're going to form an ionic bond between the magnesium ion and these two oxygens. This lowers the overall free negative charge around so nucleophiles can then come in and attack our phosphorus atom.

We're going to say the nucleophile attacks the phosphorus in the gamma position. So we have alpha, beta, gamma. So, again, remember we have our complex here this whole time. The nucleophile can then come in, attack this phosphorus, kicking the bond up to the oxygen. So here goes our nucleophile that is now attached, and it's positively charged.

Step 2, we're going to say we have a proton transfer from the positively charged nucleophile to the oxygen between the beta and gamma phosphorus atoms. So remember here this is beta, this is gamma, our nucleophile again is attached here. We're going to have a proton transfer. So now the proton is here onto this oxygen. That oxygen is making 3 bonds, so now it's positively charged.

So, again, that oxygen is positively charged because it's making too many bonds. And we're going to say here the oxygen atom pushes its lone pair to kick out ADP as the magnesium ion also is released. Alright. So remember, this whole time the magnesium ions have been attached. Here they go right here. We're going to say our oxygen wants to make a double bond again so it does, helping to kick this whole thing out.

And at the same time, we're disengaging the ionic bonds between oxygen and the magnesium because we no longer need them. So at the end, what do we create? We've created a phosphorylated nucleophile plus we've created ADP. So these would be our products at the end. We have our ADP molecule and we have our phosphorylated nucleophile.

Magnesium, it's been released, disengaged from the molecule, from the structure, so it's still hanging around within this whole reaction. Right? But this is what we care about it. At the end, we have our nucleophile that's been phosphorylated, and we have our ADP molecule.