Candidate for SFEL Travel Grant
The Yarrowia lipolytica LIP8 Lipase: Biochemical Characterization, Structural Insights and Physiological Relevance
Ahmed Aloulou1, Youssef Gargouri1 and Frédéric Carrière2
1 University of Sfax, ENIS - LBGEL, 3038 Sfax, Tunisia.
2 CNRS - Aix-Marseille Université - EIPL - UMR 7282, 13009 Marseille, France.

The lipolytic yeast Y. lipolytica is a GRAS microorganism with no adverse effect on humans, and various biotechnological applications of this yeast were investigated. Apart from biotechnological applications, Y. lipolytica provides an interesting model for studying extracellular lipolysis and fat uptake. Since Y. lipolytica can use oils as carbon sources, increasing attention has been paid to the lipases produced by this yeast. Y. lipolytica has the ability to produce large amounts of the LIP2 lipase (YLLIP2) which is assumed to be a good candidate for pancreatic enzyme replacement therapy in the treatment of pancreatic exocrine insufﬁciency. An other extracellular lipase, YLLIP8, presenting low sequence similarity with YLLIP2, was reported to be produced by Y. lipolytica. From studies performed with LIP2 and LIP8 knock-out Y. lipolytica strains, it was estimated that the lipolytic activity of YLLIP8 might contribute to only 3% of the total extracellular lipase activity of Y. lipolytica wild-type strain. It was also proposed that YLLIP8 would be mainly associated to the cell wall and could correspond to a cell-bound lipase. The present study was thus undertaken in order to better understand YLLIP8 biochemical properties. YLLIP8-wt was purified from wild-type Y. lipolytica and compared to rYLLIP8 expressed in P. pastoris. The combined effects of pH and detergents on the specific activity of YLLIP8 were investigated. Olive oil, trioctanoin and tributyrin were used as substrates in order to ascertain whether YLLIP8 does hydrolyze TAG with various chain lengths. The analysis of long-chain TAG hydrolysis variation profiles enabled to determine the regiselectivity of YLLIP8 towards long-chain TAG ester bonds. A 3D structural model revealed interesting structural features of YLLIP8.