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[EN] Lipases catalyze the hydrolysis of ester bonds in triacylglycerides, generating glycerol and free fatty acids. These enzymes are encoded by extremely complex gene families, and appear to fulfil many different biological functions. Although they are present in all types of organisms, available information on plant lipases is still very limited, as compared to their bacterial and animal counterparts. A full-length clone, BnLIP, encoding a putative lipase, has been isolated by PCR amplification of Brassica napus genomic DNA, with oligonucleotide primers derived from the sequence of an Arabidopsis thaliana homologue. The clone included an open reading frame of 1581 bp encoding a polypeptide of 526 amino acids, with a calculated molecular mass of 59.5 kDa. Analysis of the deduced protein sequence, sequence alignment with homologous proteins from related plant species, and a phylogenetic analysis revealed that the BnLIP protein belongs to the classical GxSxG-motif lipase family. RTPCR assays indicated that the BnLIP gene is expressed specifically, but only transiently, during seed germination: the lipase mRNA was not present at detectable levels in ungerminated seeds, was detected only three days after seed imbibition, but its levels decreased rapidly afterwards. No expression was observed in roots, stems or leaves of adult plants. This expression pattern suggests that BnLIP is one of the lipases involved in the hydrolysis of triacylglycerides stored in rapeseed seeds, ultimately providing nutrients and energy to sustain seedling growth until photosynthesis is activated

Lipases play an important role in lipid metabolism and are produced by a variety of species. All lipases are members of the a/â hydrolase fold super-family. Also, lipases share a conserved active site signature, the Gly-Xaa-Ser-Xaa-Gly motif. To obtain an overview of this industrially and very important class of enzymes and their characteristics, we collected and classified bacterial lipases sequences available from protein databases. Here we proposed an updated and revised classification of family I bacterial "true" lipases based mainly on a comparison of their amino acid sequences and some fundamental physicochemical and biological properties. The result of this work has identified 11 subfamilies of “true” lipases. This work will therefore contribute to a faster identification and to an easier characterization and classification of novel bacterial lipolytic enzymes. Key words : Lipases, phylogenetic analysis, lipolytic enzymes.

A recent advance in the study of plant lipases involving immunological techniques is presented. In an attempt to characterize lipases of cotyledons from germinating rapeseed seedlings and to investigate an eventual cross-reactivity with animal lipases, we have prepared anti-porcine pancreatic lipase antibodies raised in rabbit. It is shown by enzyme-linked immunosorbent assay and dot-blotting that these antibodies react with lipases in the rapeseed crude extract and in the different cellular fractions obtained by differential centrifugation. Preincubation of the antiserum with the rapeseed crude extract affects the amount of antibodies binding to the porcine pancreatic lipase. We demonstrate immunochemical cross-reactivity between rapeseed and porcine pancreatic lipase. Using the immunoblotting procedure, it is found that antibodies bind specifically to a single polypeptide with a molecular mass of about 55 kDa. Rapeseed lipase activity decreased after immunoprecipitation suggesting that antibodies were bound to some catalytic site residues. We conclude from the data obtained in this study that the two different lipase species present close similarities in amino acid sequence and antigen characteristics.*

Lipase enzymes play an important role in lipid metabolism and are produced by a variety of species. Compared with animal, bacterial and fungal, little is known about plant lipases. Although lipases belong to many different protein families, they have the same architecture, the ?/?-hydrolase fold and a conserved active site signature, the Gly-Xaa-Ser-Xaa-Gly motif. Several studies on enzymatic activity and interfacial activation phenomenon of lipases confirm the presence of consensus sequence and a conserved domain. Lipases can be divided into two main groups: carboxylesterases (EC 3.1.1.1); |true| lipases (EC 3.1.1.3), which differ in several biochemical features, which allow us to develop a database that regroups all |true| lipase proprieties to establish relationship between structure and function. LIPABASE is a centralised resource database, which provides information about |true| lipase from different species. It includes general, taxonomic, physicochemical and molecular data. Access to LIPABASE is free and available at http://www.lipabase-pfba-tun.org.

A cross-reactivity between animal and plant lipases was determined, using immunological techniques. It was shown by ELISA and dot-blotting that these antibodies react with lipases in the rapeseed crude extract and in the different cellular fractions obtained by differential centrifugation. Pre-incubation of the antiserum with the rapeseed crude extract affects the amount of antibodies binding to the porcine pancreatic lipase. Antibodies were able to precipitate lipase activity from 3-day-old rapeseed crude extract. These epitopes seem to be located in the catalytic site, suggesting that a consensus sequence exists in oleaginous lipases and that it will be universal.

Triacylglycerol lipases have been thoroughly characterized in mammals and microorganisms. By contrast, very little is known about plant lipases. In this investigation, a homology model of Arabidopsis thaliana lipase (NP_179126) was constructed using a human gastric lipase (PDB ID: 1HLG), as a template for model building. This model was then assessed for stereochemical quality and side chain environment. Natural substrates: tributyrin, trioctanoin and triolen were docked into the model to investigate ligand-substrate interaction.