Simultaneous Decrease in Deamination of 5′‐Adenylic Acid and 5′‐Deoxy‐5′‐ S ‐isobutylthioadenosine in Chick‐Embryo Fibroblasts Infected by Rous Sarcoma Virus

The rate of deamination of 5′‐deoxy‐5′‐ S ‐isobutylthioadenosine [(iBuS) 5′ Ado] in chick embryo fibroblasts was substantially reduced after their infection and morphological transformation by Rous sarcoma virus. Concomitant with the reduction in rate of (iBuS) 5′ Ado deamination there was a decrease in adenosine deaminase and 5′‐adenylic acid deaminase activities. The drop of these activities was related to infection and not to the expression of the src gene.(iBuS) 5′ Ado was deaminated by at least three enzymes or isoenzymes whose apparent molecular weights have been estimated to be 295000, 121000 and 37000 respectively. Two of these enzymes have been characterized as 5′‐adenylic acid deaminase and the heavy form of adenosine deaminase, respectively.