Cloning and sequence analysis of a polyurethane esterase of Comamonas acidovorans TB-35

Comamonas acidovorans strain TB-35 has an esterase that degrades solid polyester polyurethane (PUR). The structural gene, pudA, for the PUR esterase has now been cloned in Escherichia coli. When pudA was expressed in E. coli, the recombinant protein was able to degrade solid PUR. The predicted amino acid sequence contains the Gly-X-1-Ser-X-2-Gly motif characteristic of serine hydrolases. The highest degree of homology was detected with the Torpedo californica acetylcholinesterase (T AChE), possessing the Ser-His-Glu catalytic triad, with the glutamate residue replacing the usual aspartate residue. Similarity in the number and positions of cysteine and salt bonds was very apparent between PudA and T AChE, as were also identities of sequences and their positions in the alpha-helix and beta-strand regions between the two. In the neighborhood of the glutamate residue of the Ser(199)-His(433)-Glu(324) catalytic domain of PudA, there were three hydrophobic domains, one of which constituted the surface-binding domain, which occurred in the C-terminus of most bacterial poly(hydroxyalkanoate)(PHA) depolymerases.