Rhodococcus sp. Strain CR-53 LipR, the First Member of a New Bacterial Lipase Family (Family X) Displaying an Unusual Y-Type Oxyanion Hole, Similar to the Candida antarctica Lipase Clan

摘要

Bacterial lipases constitute the most important group of biocatalysts for synthetic organic chemistry. Accordingly, there is substantial interest in developing new valuable lipases. Considering the lack of information concerning the lipases of the genus Rhodococcus and taking into account the interest raised by the enzymes produced by actinomycetes, a search for putative lipase-encoding genes from Rhodococcus sp. strain CR-53 was performed. We isolated, cloned, purified, and characterized LipR, the first lipase described from the genus Rhodococcus. LipR is a mesophilic enzyme showing preference for medium-chain-length acyl groups without showing interfacial activation. It displays good long-term stability and high tolerance for the presence of ions and chemical agents in the reaction mixture. Amino acid sequence analysis of LipR revealed that it displays four unique amino acid sequence motifs that clearly separate it from any other previously described family of bacterial lipases. Using bioinformatics tools, LipR could be related only to several uncharacterized putative lipases from different bacterial origins, all of which display the four blocks of consensus amino acid sequence motifs that contribute to define a new family of bacterial lipases, namely, family X. Therefore, LipR is the first characterized member of the new bacterial lipase family X. Further confirmation of this new family of lipases was performed after cloning Burkholderia cenocepacia putative lipase, bearing the same conserved motifs and clustering in family X. Interestingly, all lipases grouping in the new bacterial lipase family X display a Y-type oxyanion hole, a motif conserved in the Candida antarctica lipase clan but never found among bacterial lipases. This observation contributes to confirm that LipR and its homologs belong to a new family of bacterial lipases.