ˌeɪpˌiːˈɛs ænd pˈæps ɑːɹ ˌɪntɚmˈiːdiəts ɪnðə ɹᵻdˈʌkʃən ʌv sˈʌlfeɪt tə sˈʌlfaɪt, ɐn ɛɡzəðˈɜːmɪk kənvˈɜːʒən ðæt ɪz kˈæɹid ˈaʊt baɪ sˈʌlfeɪtɹᵻdˈuːsɪŋ bæktˈɪɹiə.
APS and PAPS are intermediates in the reduction of sulfate to sulfite, an exothermic conversion that is carried out by sulfate-reducing bacteria.