So step three and step four are the two oxidative decarboxylation steps. And the enzymes that regulate these two steps are allosteric enzymes which, as we'll see in just a moment, are actually regulated by specific types of allosteric effective molecules. So the citric acid cycle has two regulatory points that are used to control its rate. And both of these points are allosteric enzymes used by the steps of the citric acid cycle, the TCA cycle. So let's quickly remember the eight different steps. In step one, we take the four carbon oxaloacetate, combined with the acetyl group of acetoco enzyme A to form a six carbon molecule known as citrate.