Practice: The reaction Fructose-6-P + ATP <===> ADP + Fructose-1,6-bisP is catalyzed by the glycolytic enzyme phosphofructokinase-1 (PFK-1). In muscle tissue, PFK-1 is a homotetramer (contains 4 identical subunits). Adenosine monophosphate (AMP) binds at a site distant from the site of catalysis on any of the four subunits & induce a conformational change that favors a relaxed & more active state of the whole tetramer. How is the role of AMP classified in this reaction?