Studies on inhibition of adenosine deaminase by isocoformycin in vitro and in vivo.
Isocoformycin is a structural isomer of coformycin which has been demonstrated to be a potent inhibitor of adenosine deaminase. Isocoformycin showed a weaker inhibition of this enzyme than coformycin; the binding of coformycin to enzyme was irreversible, but isocoformycin inhibition was competitive with substrate. The Ki value of isocoformycin was 4.5 approximately 10 X 10(-8) M. Following intraperitoneal injection of isocoformycin in mice, the adenosine deaminase activity of homogenates of several organs was determined and the following ED50 values (50% inhibition doses) were observed: 29 mg/kg for thymus, 13 mg/kg for spleen, 80 mg/kg for liver and 20 mg/kg for kidney. The inhibition of adenosine deaminase in rabbit blood in vitro was also tested in comparison with coformycin.
D000243:Adenosine Deaminase / Q000097:blood; D058892:Adenosine Deaminase Inhibitors; D000818:Animals; D003070:Coformycin / Q000097:blood*; D066298:In Vitro Techniques; D007536:Isomerism; D007700:Kinetics; D051379:Mice; D009700:Nucleoside Deaminases / Q000037:antagonists & inhibitors*; D011817:Rabbits; D012263:Ribonucleosides / Q000097:blood*
D058892:Adenosine Deaminase Inhibitors; D012263:Ribonucleosides; D003070:Coformycin; D009700:Nucleoside Deaminases; D000243:Adenosine Deaminase