SULFATE CONJUGATION OF SEROTONIN AND N-ACETYLSEROTONIN IN THE MOSQUITO, AEDES-TOGOI

The sulphate conjugation of serotonin and N-acetylserotonin (NAS) was studied in the mosquito, Aedes togoi, using a high-pressure liquid chr omatography-radioisotopic procedure. This involved the transfer of the sulphate group from 3'-phosphoadenosine-5'-phosphosulphate (PAPS-35) to serotonin or NAS by phenolsulphotransferase (PST). NAS, the acetyla ted product, is less polar than serotonin but it is a better substrate of PST. Its removal would conceivably be facilitated by sulphate conj ugation which renders it more water-soluble. This sequential two-step reaction, comprising N-acetylation of serotonin and sulphate conjugati on of the acetylated product (NAS) was also demonstrated in vitro. The developmental profile of PST activity using NAS as substrate showed t hat peak activity occurred at pupation and increased progressively for a few days after emergence of the adult. Based on the selective inhib ition of the ''P'' form of PST by 2,6-dichloro-4-nitrophenol (DCNP), t he sulphate conjugation of NAS appeared to be catalysed by the ''M'' f orm of PST.