Well, dedicated protein kinases basically phosphorylate either a single substrate molecule or a set of closely related substrate molecules. On the other hand, multifunctional protein kinases have the capability of actually catalyzing the phosphorylation of many different types of enzymes and many different types of protein molecules. Now, the first question I'd like to address is what exactly determines the specific nature of protein kinases? What exactly determines the ability of a protein kinase to actually bind and catalyze a specific location on some enzyme on some substrate molecule? Well, for a catalyzation reaction to actually take place, logically speaking, that substrate molecule has to be able to fit into the active side of that protein kinase. And not only that, the substrate molecule has to have a high enough affinity so that it remains long enough in the active side for that phosphorylation reaction to actually take place in the first place.