( ( Proteins ( -LRB- ( ( also ( called ( ( enzymes and ) polypeptides ) ) ) -RRB- ) ) ) ( ( are ( ( long chains ) ( of ( amino acids ) ) ) ) . ) )
(ROOT (S (NP (NP (NNPS Proteins)) (PRN (-LRB- -LRB-) (VP (ADVP (RB also)) (VBN called) (NP (NNS enzymes) (CC and) (NNS polypeptides))) (-RRB- -RRB-))) (VP (VBP are) (NP (NP (JJ long) (NNS chains)) (PP (IN of) (NP (JJ amino) (NNS acids))))) (. .)))
Proteins (also called enzymes and polypeptides) are long chains of amino acids.
(ROOT (S (NP (NNPS Proteins)) (VP (VBP are) (NP (NP (JJ long) (NNS chains)) (PP (IN of) (NP (JJ amino) (NNS acids))))) (. .)))