Selective Degradation of 2′-Adenylated Diadenosine Tri- and Tetraphosphates, Ap3A and Ap4A, by Two Specific Human Dinucleoside Polyphosphate Hydrolases

Selective splitting of 3'-adenylated dinucleoside polyphosphates by specific enzymes degrading dinucleoside polyphosphates.

“…Similarly, previous studies showed that 2¢-(deoxy)adenylated Ap 3 A and Ap 4 A were not substrates of the human Ap 3 A hydrolase (Guranowski et al, 2000). In contrast, both the symmetrical and asymmetrical Np 4 N¢ hydrolases are able to cleave their 3¢-adenylated substrates Ap 4 A or Gp 4 G, in line with previous findings showing the susceptibility of 2¢-deoxyadenylated Ap 4 A to the hydrolysis catalyzed by (asymmetrical) dinucleoside tetraphosphatases from human (Guranowski et al, 2000) or lupin (Maksel et al, 2001). Altogether, these results show that both types of Ap 4 A-degrading enzymes tolerate such a bulky substituent as adenylate at the 3¢ or 2¢ position of their substrates.…”

“…A. G. McLennan (Liverpool University) and D. Maksel (Melbourne University), respectively. Human Fhit protein, which is a typical dinucleoside triphosphatase (EC 3.6.1.29) (Barnes et al, 1996), overexpressed in E. coli, was obtained as described previously (Guranowski et al, 2000). Np 3 N¢ hydrolase from yellow lupin seeds (Guranowski et al, 1996), partially purified (symmetrical) Ap 4 A hydrolase (EC 3.6.1.41) from E. coli (Guranowski et al, 1983) and Ap 4 A phosphorylase (EC 2.7.7.53) from Saccharomyces cerevisiae (Guranowski & Blanquet, 1985) were obtained as described in the quoted papers.…”

“…Based on in vitro studies it has been assumed that the levels of these dinucleotides result from both their rate of synthesis by ligases and transferases (Guranowski et al, 1990;Plateau & Blanquet, 1992;Ortiz et al, 1993;Sillero & Günther Sillero, 2000) and degradation by specific and nonspecific lytic enzymes (Guranowski & Sillero, 1992;Guranowski, 2000). In addition to metabolizing Np 3 N¢s and Np 4 N¢s, the specific Np n N¢-degrading enzymes exhibit activity towards a number of Np n N¢ derivatives including: (a) Np 3 N¢s and Np 4 N¢s with various nucleosides differing both in the base and sugar moieties; (b) mRNA 5¢-cap analogues; (c) mono-and di-(N 1 ,N 6 -etheno) derivatives of Ap 3 A and Ap 4 A; (d) chain-length homologues; (e) nucleoside 5¢-tetra-and -pentaphosphates; (f) methylene-and halomethylene analogues; (g) mono-and diphosphorothioate analogues; (h) adenylated derivatives of methanetrisphosphonate; (i) diadenylated polyols (Baraniak et al, 1999;Varnum et al, 2001) and (j) 2¢-(deoxy)adenylated Ap 3 A and Ap 4 A (Guranowski et al, 2000;Maksel et al, 2001). For references concerning the compounds mentioned in (a-h) see reviews (Guranowski & Sillero, 1992;Guranowski, 2000;Blackburn et al, 1992).…”

Recent progress in the study of the intracellular functions of diadenosine polyphosphates

“…In addition to K m and k cat , the mutants were characterized by two other measurable parameters-the positional preference of cleavage of a model substrate, 2′-deoxyadenylated Ap 4 A, (2′-pdA)Ap 4 A (produced by the action of 2′,5′-oligoadenylate synthetase on Ap 4 A), and the susceptibility to fluoride inhibition. The former parameter was chosen, first because it was recently demonstrated that human Ap 4 A hydrolase easily hydrolyzes 2′-adenylated-and 2′-deoxyadenylated Ap 4 A [Guranowski et al, 2000], second because the plant counterpart exhibited the same property, and finally because the preference of cleavage of (2′-pdA)Ap 4 A by the human enzyme to the product pairs ATP + (2′-pdA)AMP (80%) rather than to (2′-pdA)ATP + AMP (20%) [Guranowski et al, 2000]). Some mutants had an altered cleavage pattern for (2′-pdA)Ap 4 A.…”

Analogs of diadenosine tetraphosphate (Ap4A).

“…Other Ap 4 A derivatives modified on the sugar moiety can be obtained from reactions supported by 2¢,5¢-poly(A) synthase, which introduces (deoxy)adenylate residue(s) onto the 2¢-(and 2¢¢¢-) position(s) of Ap 4 A (27) (Cayley & Kerr, 1982;Guranowski et al, 2000) while the recently reported poly(A) polymerase from E. coli can monoadenylate Ap 4 A at one of its two 3¢-positions (28) (Günther Sillero et al, 2001;Guranowski et al, 2003).…”