Lipases as Pathogenicity Factors of Plant Pathogens
Lipases are enzymes which hydrolyze carboxyl ester bonds in triacylglycerols liberating fatty acids and glycerol. Lipases are ubiquitous having been found in animals, plants, fungi and bacteria and they are mainly studied due to their very diverse and imp
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K. N. Timmis (ed.), Handbook of Hydrocarbon and Lipid Microbiology, DOI 10.1007/978-3-540-77587-4_248, # Springer-Verlag Berlin Heidelberg, 2010
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Lipases as Pathogenicity Factors of Plant Pathogens
Abstract: Lipases are enzymes which hydrolyze carboxyl ester bonds in triacylglycerols liberating fatty acids and glycerol. Lipases are ubiquitous having been found in animals, plants, fungi and bacteria and they are mainly studied due to their very diverse and important commercial applications. Several recent studies have shown that these enzymes are emerging as virulence associated factors in microbial plant pathogens. A number of secreted lipases form fungal plant pathogens are believed to be involved in the penetration by the fungi of plant barriers like waxes and cuticle. Internal fungal lipases on the other hand could play a role in the degradation of stored lipids and/or in signaling through the release of second messengers. Very few bacterial lipases have been studied in plant pathogens; first reports have shown that they are important virulence factors and therefore merit more attention. The role of lipases in microbial pathogenicity is just beginning to be addressed by the scientific community and initial results indicate that they could potentially be a pivotal target for disease control.
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Introduction
Microbial lipases are enzymes which hydrolyze carboxyl ester bonds present in triacylglycerols (uncharged lipids) liberating fatty acids and glycerol. Triacylglycerols display low water solubility and lipases are serine hydrolases which catalyze the reaction at the lipid-water interface, i.e., when the substrate forms an emulsion (Gupta et al., 2004; Jaeger et al., 1994). Lipases are most often secreted by micro-organisms and they convert the water-insoluble glycerides into compounds which can be readily taken up by cells. Lipases from different micro-organisms display rather low conservation in their primary structure. The structural catalytic site is well defined and is most commonly composed of a triad consisting of Ser-AspHis and the consensus sequence Gly-x-Ser-x-Gly is found at the serine active site. The determination of several three-dimensional structures of lipases revealed that they belong to the family of a/b-hydrolase fold enzymes (Nardini and Dijkstra, 1999). Many lipases from different microbial species have been isolated and studied mainly due to their important biotechnological applications (Gupta et al., 2004; Jaeger et al., 1994; Jaeger and Reetz, 1998). In fact lipases have major commercial importance in the detergent, pharmaceutical, pulp and paper and food ingredients industry; in addition ongoing research aims to increase the number of potential applications. Interestingly, recent studies have evidenced that lipases are involved in pathogenicity in several microbial plant pathogens. The scope of this chapter is to review and discuss current knowledge on the emerging role of lipases as plant associated virulence factors. The fungal and bacterial lipases will be discussed sepa
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