Further studies on 5'-Nucleotidase from serum of liver cirrhotic individuals.
The kinetic properties of 5'-Nucleotidase  were investigated in untreated patients with liver cirrhosis at 37 degrees C. Mg+2 and Mn+2 were found to activate both normal and liver cirrhotic 5'-Nucleotidase, but Nickel inhibited the enzyme in both systems competitively. Both ATP and adenosine act as inhibitors to 5'-Nucleotidase. The inhibitory constant for ATP was different in normal and liver cirrhotic individuals, 0.1 +/- 0.03 for normal and 0.225 +/- 0.02 for liver cirrhosis. In our investigation, ATP was found to be a competitive inhibitor of 5'-Nucleotidase which compete the substrate (A-5'-MP) for the active site. Inhibition of 5'-Nucleotidase by adenosine is of non-competitive type, for both normal and liver cirrhotic sera. It was observed that both serum 5'-Nucleotidase exhibited pH dependent characteristics; in that there was an optimum substrate concentration at each pH value and the plot of pKm versus pH shows great dependency of km on pH.
D000241:Adenosine / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000494:pharmacology; D004789:Enzyme Activation; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008103:Liver Cirrhosis / Q000201:enzymology*; D008345:Manganese / Q000494:pharmacology; D009532:Nickel / Q000494:pharmacology; D009708:Nucleotidases / Q000037:antagonists & inhibitors / Q000097:blood*
D008345:Manganese; D009532:Nickel; D000255:Adenosine Triphosphate; D009708:Nucleotidases; D000241:Adenosine