Effects of adenine nucleotides on low Km 5' nucleotidase from human seminal plasma

1. Low Km 5' nucleotidase purified from human seminal plasma has been used in this study to investigate the response of the enzyme ot adenine nucleoside di- and triphosphates in the presence of AMP and IMP as substrates. 2. In the presence of AMP, the addition of 0.5 mM ATP to the enzyme Mg-free results into the highest Vmax/Km ratio value and other experimental combinations of effectors tested cause variation of the kinetic parameters of the enzyme, indicating a control of AMP dephosphorylation by adenine nucleotides. 3. In the presence of IMP, ATP and ADP activate the enzyme but the response to various experimental combinations of effectors shows no significant difference in the kinetic properties of the enzyme, indicating a different control of the dephosphorylation of IMP.