Synthesis of (di)nucleoside polyphosphates by the ubiquitin activating enzyme E1.
Previous work from this laboratory had shown that ligases may catalyze the synthesis of (di)nucleoside polyphosphates. Here, we show that one of the enzymes of the proteasome system (E1 or the ubiquitin (Ub) activating enzyme, EC 6.3.2.19) catalyzes very effectively (k(cat) = 0.29+/-0.05 s(-1)) the transfer of AMP from the E-AMP-ubiquitin complex to tripolyphosphate or tetrapolyphosphate with formation of adenosine tetra- or pentaphosphate (p4A or p5A), respectively. Whereas the concomitant formation of AMP is stimulated by the presence of dithiothreitol in a concentration dependent manner, the synthesis of p4A is only slightly inhibited by this compound. Previous treatment of the enzyme (E1) with iodoacetamide inhibited only partially the synthesis of p4A. p4A can substitute for ATP as substrate of the reaction to generate the ubiquityl adenylate complex. A small amount of diadenosine pentaphosphate (Ap5A) was also synthesized in the presence of p4A.
Günther Sillero
Maria A
MA
Departamento de Bioquímica, Instituto de Investigaciones Biomédicas Alberto Sols UAM/CSIC, Facultad de Medicina, 28029 Madrid, Spain.
de Diego
Anabel
A
Silles
Eduardo
E
Sillero
Antonio
A
D000249:Adenosine Monophosphate / Q000096:biosynthesis; D015226:Dinucleoside Phosphates / Q000096:biosynthesis*; D004229:Dithiothreitol / Q000494:pharmacology; D007460:Iodoacetamide / Q000494:pharmacology; D044764:Ubiquitin-Activating Enzymes / Q000037:antagonists & inhibitors / Q000737:chemistry*
D015226:Dinucleoside Phosphates; D000249:Adenosine Monophosphate; D044764:Ubiquitin-Activating Enzymes; D004229:Dithiothreitol; D007460:Iodoacetamide