Serine/threonine-specific protein kinase Tags: Enzyme.A serine/threonine protein kinase (EC 2.7.11.1) is a kinase enzyme that phosphorylates the OH group of serine or threonine (which have similar sidechains). At least 125 of the 500+ human protein kinases are serine/threonine kinases (STK). thumbnail EC number 2.7.11.1 Learn more... Loading...