“ Ca2+ (maintained at 10 muM by a Ca2+ buffer) decreased the S0.5 for alpha-ketoglutarate 63-fold (from 25 to 0.40 mM); even in the presence of a positive effector, ADP or phosphate, Ca2+ decreased the S0.5 for alpha-ketoglutarate 7.8- or 28-fold, respectively.”
“Consistent with a mechanism of action dependent of Ca2+, …) or phosphate (20 mM) reduced the S0.5 for alpha-ketoglutarate … Ca2+ ( i.e., 4.5- or 1.67-fold, respectively); however, these effectors elicited larger decreases … in the absence of Ca2+ (i.e., 37- or 3.7-fold, respectively).”