RING-MODIFIED SUBSTRATES OF ADENOSINE DEAMINASES

Adenosine deaminases (adenosine aminohydrolase, EC 3.5.4.4) from the mould Aspergillus oryzae and from calf intestine catalyze deamination of 4-aminopteridine, 1-methyladenosine, 3-β-(D-ribofuranosyl)adenine, and unsubstituted adenine. Unsubstituted pteridine is an effective inhibitor of both enzymes. When adenine derivatives are compared, electron-with- drawing groups are found to increase the limiting rate of enzymatic deamination. The presence of ribose as a substituent on either the 3 or the 9 position, or the replacement of the 8-carbon by sulfur or oxygen, result in large increases in Vmax as compared with adenine. Similarly, 8-trifluoromethylpurine is a much more effective inhibitor than unsubstituted purine. © 1969, American Chemical Society. All rights reserved.