'- Ph osph o aden os ine - 5 '- ph osph os ulf ate ▁( P AP S ) ▁is ▁a ▁derivative ▁of ▁ad en os ine ▁mon oph osph ate ▁that ▁is ▁ph osph ory l ated ▁at ▁the ▁ 3 ' ▁position ▁and ▁has ▁a ▁sul f ate ▁group ▁attached ▁to ▁the ▁ 5 ' ▁ph osph ate . ▁ ▁It ▁is ▁the ▁most ▁common ▁co enz yme ▁in ▁sul f otr ans fer ase ▁re actions . ▁It ▁is ▁end ogen ously ▁synth es ized ▁by ▁organ isms ▁via ▁the ▁ph osph ory lation ▁of ▁ad en os ine ▁ 5 '- ph osph os ulf ate ▁( AP S ), ▁an ▁inter medi ary ▁met abol ite . ▁In ▁humans ▁such ▁reaction ▁is ▁performed ▁by ▁b if unction al ▁ 3 '- ph osph o aden os ine ▁ 5 '- ph osph os ulf ate ▁synth ases ▁( P AP SS 1 ▁and ▁P AP SS 2 ) ▁using ▁ATP ▁as ▁the ▁ph osph ate ▁don or . ▁ ▁Form ation ▁and ▁reduction ▁A PS ▁and ▁P AP S ▁are ▁inter medi ates ▁in ▁the ▁reduction ▁of ▁sul f ate ▁to ▁sul f ite , ▁an ▁ex oth erm ic ▁conversion ▁that ▁is ▁carried ▁out ▁by ▁sul f ate - redu cing ▁b acter ia . ▁In ▁these ▁organ isms , ▁sul f ate ▁serves ▁as ▁an ▁electron ▁accept or , ▁a kin ▁to ▁the ▁use ▁of ▁O 2 ▁as ▁an ▁electron ▁accept or ▁by ▁aer ob