But what exactly activates this phosphorlase kinase? Well, before we look at that question, let's actually discuss what the structure of phosphorase kinase actually is. Well, the structure of this kinase actually consists of four different types of subunits, four different types of polypeptide chains. We have the alpha, the beta, the gamma and the delta. And we actually have four of each type. So this is what the structure looks like.