Synthesis of diadenosine 5′,5‴‐P1,P4‐tetraphosphate by organellar and cytoplasmic phenylalanyl‐tRNA synthetases of Euglena gracilis

Abstract

Purified phenylalanyl-tRNA synthetases present in chloroplasts, mitochondria and cytoplasm of green and bleached Euglena gracilis strains, respectively, are able to synthesize diadenosine 5′,5‴-P¹,P⁴-tetraphosphate (Ap₄A). Ap₄A synthesis is strictly dependent on zinc ions. This is the first evidence that chloroplasts should be able to synthesize Ap₄A. Synthesis of Ap₄A by phenylalanyl-tRNA synthetases of the three compartments of a plant cell or by other enzymes such as Ap₄A phosphorylase is discussed.