( ( Explain ( why ( enzymes ( have ( ( an ( optimum ( ( temperature and ) pH ) ) ) ( for ( their activity ) ) ) ) ) ) ) . )
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Explain why enzymes have an optimum temperature and pH for their activity.
(ROOT (S (NP (DT All) (NNS enzymes)) (VP (VBP have) (NP (DT an) (JJ optimal) (NN temperature) (CC and) (NN ph.)))))