. "In the second step of PAPS biosynthesis, adenylyl sulfate is phosphorylated. This reaction is energetically favorable, and makes the overall PAPS synthesis energetically favorable as well."^^ . . . . . . . . "adenylyl sulfate (APS) + ATP => PAPS + ADP"^^ . "APS reacts with another ATP molecule to form PAPS"^^ . "2.7.1.25"^^ . . . . .