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    Galactolipase activity of Talaromyces thermophilus lipase on galactolipid micelles, monomolecular films and UV-absorbing surface-coated substrate

    Year: 2018

    Journal: Biochim. Biophys. Acta Mol. Cell Biol. Lipids, Volume 1863, SEP, page 1006–1015

    Authors: Belhaj, Ines; Amara, Sawsan; Parsiegla, Goetz; Sutto-Ortiz, Priscila; Sahaka, Moulay; Belghith, Hafedh; Rousset, Audric; Lafont, Dominique; Carriere, Frederic

    Organizations: Agence Nationale de la Recherche in the framework of the GALACTOLIPASE project [ANR-09-CP2D-06-01]; Ministry of Higher Education and Scientific Research, Tunisia; Laboratoire de Biotechnologie Moleculaire des Eucaryotes du Centre de Biotechnologie de Sfax

    Keywords: Enzyme assay; Galactolipid; Galactolipase; In silico docking; Lipase; Monomolecular films

    Talaromyces thermophilus lipase (TTL) was found to hydrolyze monogalactosyl diacylglycerol (MGDG) and digalactosyl diacylglycerol (DGDG) substrates presented in various forms to the enzyme. Different assay techniques were used for each substrate: pHstat with dioctanoyl galactolipid-bile salt mixed micelles, barostat with dilauroyl galactolipid monomolecular films spread at the air-water interface, and UV absorption using a novel MGDG substrate containing a-eleostearic acid as chromophore and coated on microtiter plates. The kinetic properties of TTL were compared to those of the homologous lipase from Thermomyces lanuginosus (TLL), guinea pig pancreatic lipase-related protein 2 and Fusarium solani cutinase. TTL was found to be the most active galactolipase, with a higher activity on micelles than on monomolecular films or surface-coated MGDG. Nevertheless, the UV absorption assay with coated MGDG was highly sensitive and allowed measuring significant activities with about 10 ng of enzymes, against 100 ng to 10 mu g with the pHstat. TTL showed longer lag times than TLL for reaching steady state kinetics of hydrolysis with monomolecular films or surface-coated MGDG. These findings and 3D-modelling of TTL based on the known structure of TLL pointed out to two phenylalanine to leucine substitutions in TTL, that could be responsible for its slower adsorption at lipid-water interface. TTL was found to be more active on MGDG than on DGDG using both galactolipid-bile salt mixed micelles and galactolipid monomolecular films. These later experiments suggest that the second galactose on galactolipid polar head impairs the enzyme adsorption on its aggregated substrate.
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