title: Extracellular lipase of an entomopathogenic fungus effecting larvae of a scale insect.
abstract: Lipases play an important role in the infection process of entomopathogenic fungi by hydrolyzing the ester bonds of lipoproteins, fats and waxes present on the insect surface and in the body. Here we report the purification and characterization of an extracellular lipase from Isaria fumosorosea. The enzyme was purified (138.46-fold) in three steps using (NH4 )2 SO4 precipitation followed by DEAE-cellulose and Sephadex G-100 column chromatography. The molecular weight of purified enzyme was determined to be 31 KDa by SDS-PAGE. The optimum temperature and pH for enzyme activity were 35 °C and 7.0, respectively, using p-nitrophenylpalmitate as the substrate. Lipolytic activity was enhanced in the presence of Ca(+2) , Mg(+2) , Na(+) , and NH4 (+) salts, while Zn(+2) , Fe(+2) , and Cu(+2) inhibited enzyme activity. The enzyme displayed broad substrate specificity with the highest activity observed for coconut oil and p-nitrophenyl carprate. Topical co-application of purified lipase with fungal conidial suspensions decreased the median survival time (ST50 ) of Dysmicoccus neobrevipes nymphs as compared to the fungus alone. Our results indicate that an extracellular lipase produced by I. fumosorosea can be exploited for development of enzyme-based insect management.
authors.affiliation: Engineering Research Center of Bhological Control, Ministry of Education, College of Natural Resource and Environment, South China Agricultural University. Wushan Road, Guangzhou City, P. R., China.
authors.forename: Shaukat
authors.initials: S
authors.lastname: Ali
authors.forename: Shunxiang
authors.initials: S
authors.lastname: Ren
authors.forename: Zhen
authors.initials: Z
authors.lastname: Huang
mesh_terms: D000818:Animals; D001681:Biological Assay; D011232:Chemical Precipitation; D002853:Chromatography, Liquid; D004591:Electrophoresis, Polyacrylamide Gel; D020536:Enzyme Activators / Q000032:analysis; D004795:Enzyme Stability; D006863:Hydrogen-Ion Concentration; D006999:Hypocreales / Q000201:enzymology*; D007313:Insecta / Q000382:microbiology* / Q000502:physiology*; D007814:Larva / Q000382:microbiology / Q000502:physiology; D008049:Lipase / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism*; D008970:Molecular Weight; D010572:Pest Control, Biological / Q000379:methods; D013379:Substrate Specificity; D016019:Survival Analysis; D013696:Temperature
chemical_list: D020536:Enzyme Activators; D008049:Lipase
keywords: Biological control; Dysmicoccus neobrevipes; Entomopathogenic fungus; Enzyme purification; Temperature; pH