Investigations into the origin of the molecular recognition of several adenosine deaminase inhibitors.
Inhibitors of adenosine deaminase (ADA, EC 3.5.4.4) are potential therapeutic agents for the treatment of various health disorders. Several highly potent inhibitors were previously identified, yet they exhibit unacceptable toxicities. We performed a SAR study involving a series of C2 or C8 substituted purine-riboside analogues with a view to discover less potent inhibitors with a lesser toxicity. We found that any substitution at C8 position of nebularine resulted in total loss of activity toward calf intestinal ADA. However, several 2-substituted-adenosine, 8-aza-adenosine, and nebularine analogues exhibited inhibitory activity. Specifically, 2-Cl-purine riboside, 8-aza-2-thiohexyl adenosine, 2-thiohexyl adenosine, and 2-MeS-purine riboside were found to be competitive inhibitors of ADA with K(i) values of 25, 22, 6, and 3 μM, respectively. We concluded that electronic parameters are not major recognition determinants of ADA but rather steric parameters. A C2 substituent which fits ADA hydrophobic pocket and improves H-bonding with the enzyme makes a good inhibitor. In addition, a gg rotamer about C4'-C5' bond is apparently an important recognition determinant.
Department of Chemistry, Gonda-Goldschmied Medical Research Center, Bar-Ilan University, Ramat-Gan, Israel.
Irina
I
Gillerman
Bilha
B
Fischer
D000241:Adenosine / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry*; D000243:Adenosine Deaminase / Q000737:chemistry*; D058892:Adenosine Deaminase Inhibitors / Q000138:chemical synthesis / Q000737:chemistry*; D000818:Animals; D001372:Aza Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D002417:Cattle; D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D008958:Models, Molecular; D008968:Molecular Conformation; D011684:Purine Nucleosides / Q000138:chemical synthesis / Q000737:chemistry*; D012263:Ribonucleosides / Q000138:chemical synthesis / Q000737:chemistry*; D013237:Stereoisomerism; D013329:Structure-Activity Relationship
D058892:Adenosine Deaminase Inhibitors; D001372:Aza Compounds; D011684:Purine Nucleosides; D012263:Ribonucleosides; C005248:nebularine; D000243:Adenosine Deaminase; D000241:Adenosine