Effect of analogues of 5'-methylthioadenosine on cellular metabolism. Inactivation of S-adenosylhomocysteine hydrolase by 5'-isobutylthioadenosine.
The effects of a number of nucleosides related to 5'-methylthioadenosine on the activities of S-adenosylhomocysteine hydrolase, 5'-methylthioadenosine phosphorylase, spermidine synthase and spermine synthase were investigated. Both 5'-methylthioadenosine and 5'-isobutylthioadenosine gave rise to an enzyme-activated irreversible inhibition of S-adenosylhomocysteine hydrolase, but 5'-methylthiotubercidin (5'-methylthio-7-deaza-adenosine), 5'-deoxy-5'-chloroformycin, 5'-ethylthio-2-fluoro-adenosine and 1,N6-etheno-5'-methylthioadenosine were totally ineffective in producing this inactivation. Of the nucleosides tested, only 5'-methylthioadenosine, 5'-methylthiotubercidin and 5'-isobutylthioadenosine were inhibitory towards the aminopropyltransferases responsible for the synthesis of spermine and spermidine. 5'-Methylthiotubercidin, 5'-deoxy-5'-chloroformycin and 5'-isobutylthioadenosine were inhibitors of the degradation of 5'-methylthioadenosine by 5'-methylthioadenosine phosphorylase, but only 5'-isobutylthioadenosine was also a substrate for this enzyme. These results suggest that the effects of 5'-isobutylthioadenosine of the cell may result from the combination of inhibitory actions on polyamine synthesis, 5'-methylthioadenosine degradation and S-adenosylhomocysteine degradation. The resulting increased concentrations of S-adenosylhomocysteine could bring about inhibition of methyltransferase reactions. A new convenient method for the assay of S-adenosylhomocysteine hydrolase in the direction of synthesis is described.
D000241:Adenosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D043383:Adenosylhomocysteinase; D000818:Animals; D003839:Deoxyadenosines / Q000031:analogs & derivatives* / Q000494:pharmacology; D005573:Formycins / Q000494:pharmacology; D006710:Homocysteine / Q000494:pharmacology; D006867:Hydrolases / Q000037:antagonists & inhibitors*; D011683:Purine-Nucleoside Phosphorylase / Q000037:antagonists & inhibitors; D051381:Rats; D011436:Spermidine Synthase / Q000037:antagonists & inhibitors; D013097:Spermine Synthase / Q000037:antagonists & inhibitors; D013872:Thionucleosides / Q000494:pharmacology*
D003839:Deoxyadenosines; D005573:Formycins; D013872:Thionucleosides; D006710:Homocysteine; C013919:5'-deoxy-5'-S-isobutylthioadenosine; C008500:5'-methylthioadenosine; C038330:5'-deoxy-5'-chloroformycin; D011683:Purine-Nucleoside Phosphorylase; C021784:5'-methylthioadenosine phosphorylase; D011436:Spermidine Synthase; D013097:Spermine Synthase; D006867:Hydrolases; D043383:Adenosylhomocysteinase; D000241:Adenosine