Nucleoside Triphosphates and Higher Phosphates

The corresponding triphosphates of the other ribonucleotides, that is, CTP, GTP, UTP and TTP, like ATP, are phosphorylating agents and all play important roles in bio processes. 

Adenosine tetraphosphate (AP4) (10.112a) and pentaphosphate (Apj) (10.112b) have been identified from several sources, but they do not substitute for ATP (Apj) in phosphorylation reactions and their biochemical role is largely unknown [88,89]. 

Di-adenosine (10.113a) and di-guanosine (10.113b) tetraphosphales have been isolated from natural sources and appear to be present in most cells. Their biochemical role is unknown [90]. 

Guanosine 5 -diphosphate 3 -diphosphate (10.114a), andguanosine 5 -triphosphate 3 -diphosphate (10.114b) are formed in cells from ATP and GTP under conditions of amino acid starvation. 

Doubly linked nucleotides occur in c-diguanilic acid (10.115), a regulator of cellulose bacterial synthesis [91]. 

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