AMP-deaminase from human term placenta.

AMP-deaminase from human term placenta was chromatographed on a phosphocellulose column and physico-chemical and immunological properties of the purified enzyme were investigated. At physiological pH 7.0, in the absence of regulatory ligands (control conditions) studied AMP-deaminase manifested sigmoid-shaped substrate saturation kinetics, with half-saturation parameter (S0.5) value of about 7 mM. Addition of important allosteric effectors (ATP, ADP or orthophosphate) modified kinetic properties of studied AMP-deaminase, influencing mainly the value of S0.5, parameter. Micromolar concentrations of stearylo-CoA inhibited potently the enzyme making it no longer sensitive towards 1 mM ATP-induced activation. SDS-PAGE electrophoresis of the purified enzyme revealed presence of 68 kDa protein fragment, reacting with anti-(human) liver AMP-deaminase antibodies. Experimental results presented indicate that 'liver type' of AMP-deaminase is an enzyme form present in human term placenta.