ic ▁organ isms . ▁Sul f ate ▁is ▁not ▁reduced ▁directly ▁but ▁must ▁be ▁activ ated ▁by ▁the ▁formation ▁of ▁A PS ▁or ▁P AP S . ▁These ▁carri ers ▁of ▁activ ated ▁sul f ate ▁are ▁produced ▁by ▁reaction ▁with ▁ATP . ▁ ▁The ▁first ▁reaction ▁is ▁catal ys ed ▁by ▁ATP ▁sul f ury l ase : ▁SO 4 2 − ▁ ▁+ ▁ATP ▁▁ ▁→ ▁▁ ▁A PS ▁ ▁+ ▁ ▁P Pi ▁The ▁conversion ▁of ▁A PS ▁to ▁P AP S ▁is ▁catal ys ed ▁by ▁A PS ▁kin ase : ▁A PS ▁ ▁+ ▁ ▁ATP ▁ ▁→ ▁ ▁P AP S ▁ ▁+ ▁AD P ▁ ▁Red u ction ▁of ▁A PS ▁leads ▁to ▁sul f ite , ▁which ▁is ▁further ▁reduced ▁to ▁hydro gen ▁sul f ide , ▁which ▁is ▁ex cret ed . ▁ ▁This ▁process ▁is ▁called ▁dis sim il atory ▁sul f ate ▁reduction . ▁ ▁Red u ction ▁of ▁P AP S , ▁a ▁more ▁elabor ated ▁sul f ate ▁est er , ▁leads ▁also ▁to ▁hydro gen ▁sul f ide . ▁ ▁But ▁in ▁this ▁case , ▁the ▁product ▁is ▁used ▁in ▁b ios yn thesis , ▁e . g . ▁for ▁the ▁production ▁of ▁c yst e ine . ▁ ▁The ▁latter ▁process ▁is ▁called ▁assim il atory ▁sul f ate ▁reduction ▁because ▁the ▁sul f ate ▁sul fur ▁is ▁assim il ated . ▁ ▁References ▁ ▁Category : N uc le ot ides ▁Category : Co enz ym es