Quantitative study of lipase secretion, extracellular lipolysis, and lipid storage in the yeast Yarrowia lipolytica grown in the presence of olive oil: analogies with lipolysis in humans |
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Authors: | Najjar Amal Robert Sylvie Guérin Clémence Violet-Asther Michèle Carrière Frédéric |
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Institution: | (1) Enzymologie Interfaciale et Physiologie de la Lipolyse, UPR 9025, CNRS, Aix-Marseille Universit?, 31 Chemin Joseph Aiguier, 13402 Marseille, France;(2) GERME S.A., 27 Boulevard Charles Moretti, 13014 Marseille, France; |
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Abstract: | Lipase secretion, extracellular lipolysis, and fatty acid uptake were quantified in the yeast Yarrowia lipolytica grown in the presence of olive oil and/or glucose. Specific lipase assays, Western blot analysis, and ELISA indicated that
most of the lipase activity measured in Y. lipolytica cultures resulted from the YLLIP2 lipase. Lipase production was triggered by olive oil and, during the first hours of culture,
most of the lipase activity and YLLIP2 immunodetection remained associated with the yeast cells. YLLIP2 was then released
in the culture medium before it was totally degraded by proteases. Olive oil triglycerides were largely degraded when the
lipase was still attached to the cell wall. The fate of lipolysis products in the culture medium and inside the yeast cell,
as well as lipid storage, was investigated simultaneously by quantitative TLC–FID and GC analysis. The intracellular levels
of free fatty acids (FFA) and triglycerides increased transiently and were dependent on the carbon sources. A maximum fat
storage of 37.8% w/w of yeast dry mass was observed with olive oil alone. A transient accumulation of saturated FFA was observed whereas intracellular
triglycerides became enriched in unsaturated fatty acids. So far, yeasts have been mainly used for studying the intracellular
synthesis, storage, and mobilization of neutral lipids. The present study shows that yeasts are also interesting models for
studying extracellular lipolysis and fat uptake by the cell. The quantitative data obtained here allow for the first time
to establish interesting analogies with gastrointestinal and vascular lipolysis in humans. |
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