Selenophosphat

Selenophosphate is the anion of selenophosphoric acid and serves as the activated selenium donor in biological selenocysteine biosynthesis. It is a small, highly reactive phosphorus–selenium oxyanion generated in cells by selenophosphate synthetase (SPS) from selenide and ATP, yielding selenophosphate, AMP, and pyrophosphate.

In bacteria, selenocysteine synthase (SelA) uses selenophosphate to convert Ser-tRNASec into Sec-tRNASec, enabling cotranslational incorporation of selenocysteine at UGA codons in selenoproteins. In archaea and eukaryotes, a related enzyme complex (SepSecS) participates in Sec-tRNASec formation with selenophosphate as the selenium donor, while additional factors assist in recruiting Sec-tRNASec to the ribosome and recognizing UGA recoding signals.

Selenophosphate is primarily associated with organisms that synthesize selenoproteins. It is typically transient and highly reactive under physiological conditions, and is usually studied in the context of enzymatic pathways rather than isolated as a stable compound. Its production and consumption are tightly coordinated within selenium metabolism and protein synthesis, reflecting its central role as the source of selenium for selenocysteine incorporation during translation.