And so it has different active sites. It has more than one active side. It has more than one side to which the oxygen actually binds to. And so because of that, every time an oxygen binds onto one of the sites, it basically creates a conformational change in the structure of that enzyme. And that induces it increases the affinity of the other sites for that same substrate, for that oxygen molecule. And so what that implies is the reason ATCAs exhibits cooperative behavior is because it consists of multiple subunits, and those subunits must have additional active sites.