Thiophosphates and Phosphoramidates

Thiophosphates and Phosphoramidates.—Adenosine 5 -0-(l-thiodiphosphate) (19a) and adenosine 5 -0-(2-thiodiphosphate) (19b) are not phosphorylated by ATP synthetase in oxidative phosphorylation, but are potent inhibitors of 

When ATP and 2,4,6-trinitrobenzenesulphonic acid are mixed at pH 9.5, 2 - (or 3 -) 0-(2,4,6-trinitrophenyl)adenosine-5 -triphosphate (22) is formed, which binds to, and is hydrolysed by, heavy meromyosin. This ATP derivative exhibits reversible formation of a Meisenheimer complex, with pK 5.1. The 

The reaction of 5 -amino-5 -deoxyadenosine with trimetaphosphate affords the 5 -Af-triphosphate (23). When (23) is employed as substrate with glucose in the hexokinase-catalysed reaction, the 5 -AT-diphosphate (24) is obtained the latter is cleaved by snake venom phosphodiesterase to the 5 -phosphoramidate, and hydrolyses in acid to the amino-nucleoside. It does not appear to be polymerized by polynucleotide phosphorylase. In this context it is noteworthy that uridine 5 -5-thiopyrophosphate (25) is a competitive inhibitor for polynucleotide phosphorylase from E. coli, but not a substrate, and that the 5 -S-thiotriphosphates (26) and (27) show neither substrate nor inhibitory properties for RNA polymerase or DNA polymerase I, respectively. However, (23) can be polymerized using the latter enzyme, showing that the introduction of a 5 -heteroatom does not completely exclude these modified nucleotides as substrates for the polymerizing enzymes. 

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