“…In addition, it has been shown that K ϩ changes the kinetic mechanism of rabbit muscle pyruvate kinase and is involved in the acquisition of the active conformation of the enzyme (20 (21), a water molecule, and a phosphate oxygen of phosphoenolpyruvate analogs (22), or an oxygen from the ␥-phosphate of ATP (5). For a long time, it was thought that the absolute dependence of K ϩ was a common feature to all pyruvate kinases (8,(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38). However, as the number of characterized enzymes increased, it became apparent that the activity of several pyruvate kinases was K ϩ -independent, for example those from Escherichia coli (Type II) (39), Phycomyces blakesleeanus (40), Corynebacterium glutamicum (41), Zymomonas mobilis (42), Thermoproteus tenax (43), Synechococcus pcc 6301 (44), Archaeoglobus fulgidus, Pyrobaculum aerophilum, Aeropyrum pernix, and Thermotoga maritima (45).…”