Comparison of PaeX with its homologues. The PaeX sequence, from residues 80 to 322 (“PaeX E. ch”), is aligned with the C-terminal domain of a B. fibriosolvens xylanase (X61495) (“XynB B. fi”) and with a hypothetical protein of C. crescentus (AAK24284.1) (“Hyp C. cr”). The residues conserved in all the sequences are given below the alignment. The residues corresponding to the G-S-G motif of serine hydrolases are underlined. The arrowheads point to the conserved residues, S, D, and H, predicted to constitute the catalytic triad of a serine hydrolase.