( ( Enzyme Proteins ) ( ( ( that act ) as ) ( ( ( catalysts , ) ( ( ( speeding ( ( the rate ) ( ( at which ) ( ( biochemical reactions ) proceed ) ) ) ) ( but not ) ) ( altering ( ( the ( ( direction or ) nature ) ) ( of ( the reactions ) ) ) ) ) ) . ) ) )
(ROOT (S (NP (NNP Enzyme) (NNPS Proteins)) (ADVP (NP (DT that) (NN act)) (RB as)) (VP (VBZ catalysts) (, ,) (S (VP (VP (VBG speeding) (NP (NP (DT the) (NN rate)) (SBAR (WHPP (IN at) (WHNP (WDT which))) (S (NP (JJ biochemical) (NNS reactions)) (VP (VBP proceed)))))) (CONJP (CC but) (RB not)) (VP (VBG altering) (NP (NP (DT the) (NN direction) (CC or) (NN nature)) (PP (IN of) (NP (DT the) (NNS reactions)))))))) (. .)))
Enzyme Proteins that act as catalysts, speeding the rate at which biochemical reactions proceed but not altering the direction or nature of the reactions.
(ROOT (S (PP (IN In) (NP (DT a) (JJ biological) (NN reaction))) (, ,) (NP (NNS proteins)) (VP (VBP act) (PP (IN as) (NP (NNS catalysts)))) (. .)))