Structure-Function Studies on Cutinase, a Small Lipolytic Enzyme with a Water Accessible Active Site
Cutinases are enzymes of 22-26 KDa which are able to hydrolyse ester bonds in the cutin polymer (Kolattukudy, 1984). Cutinases are produced by several phytopathogenic fungi and pollen (Ettinger et aL, 1987). For many years, cutinases have been thought to play a crucial role in the fungal invasion of host plants: the hydrolysis of cutin, an insoluble monocarboxylic acid polyester representing the main component of the plant cuticle, has been thought to enable the penetration of the fungus in the plant. However, interpretations of recent data on fungal cutinase activity and pathogenicity are contradictory, and range from cutinase having little or no influence at all on pathogenicity, to it enhancing adhesion of fungal spores to the plant surface (Schafer, 1993). In addition to cutin polymer degradation, cutinases are also able to hydrolyse a large variety of synthetic esters and show activity on short and long chains of emulsified triacylglycerols as efficiently as pancreatic lipases (Table 1a). Contrary to lipases, the activity of which is greatly enhanced in the presence of a lipid/water interface, cutinases do not display, or display little, interfacial activation, being active on both soluble and emulsified triglycerides (Sarda & Desnuelle, 1958; Verger & de Haas, 1976) (Table 1b).