Parapouli et al. analysed a new thermostable alkaliphilic lipase LipSm from Stenotrophomonas maltophilia. It lacks the requirement for interfacial activation for small substrates. They created a new family XIX of updated classification for homologues of this enzyme. This family is not separated yet from Fungal-Bact_LIP together with Family_XVII and Family_X.2 in ESTHER
Background: Microbial lipases catalyze a broad spectrum of reactions and are enzymes of considerable biotechnological interest. The focus of this study was the isolation of new lipase genes, intending to discover novel lipases whose products bear interesting biochemical and structural features and may have a potential to act as valuable biocatalysts in industrial applications. Results: A novel lipase gene (lipSm), from a new environmental Stenotrophomonas maltophilia strain, Psi-1, originating from a sludge sample from Psittaleia (Greece), was cloned and sequenced. lipSm was further overexpressed in E. coli BL21(DE3) and the overproduced enzyme LipSm was purified and analyzed in respect to its biochemical and kinetic properties. In silico analysis of LipSm revealed that it is taxonomically related to several uncharacterized lipases from different genera, which constitute a unique clade, markedly different from all other previously described bacterial lipase families. All members of this clade displayed identical, conserved consensus sequence motifs, i.e. the catalytic triad (S, D, H), and an unusual, amongst bacterial lipases, Y-type oxyanion hole. 3D-modeling revealed the presence of a lid domain structure, which allows LipSm to act on small ester substrates without interfacial activation. In addition, the high percentage of alanine residues along with the occurrence of the AXXXA motif nine times in LipSm suggest that it is a thermostable lipase, a feature verified experimentally, since LipSm was still active after heating at 70 degrees C for 30 min. Conclusions: The phylogenetic analysis of LipSm suggests the establishment of a new bacterial lipase family (XVIII) with LipSm being its first characterized member. Furthermore, LipSm is alkaliphilic, thermostable and lacks the requirement for interfacial activation, when small substrates are used. These properties make LipSm a potential advantageous biocatalyst in industry and biotechnology. PMID 29942797 Parapouli_2018_J.Biol.Res.(Thessalon)_25_10 corrects the number XVIII in XIX because Samoylova_2018_Extremophiles_22_271 had already use number XVIII PMID 29330648
