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Amal Kamil Najjar

Assistant professor
Chemistry - Biochemistry department - Section II - Fanar
Speciality: Chemistry
Specific Speciality: Microbio et Biotechno. Pr le développ.

Positions
Teaching 4 Taught Courses
(2014-2015) Bioc 240 - Basic Biochemistry Lab

BS Biochemistry

(2014-2015) Bioc 281 - Structural Biochemistry

BS Chemistry

(2014-2015) Bioc 331 - Modulation of Protein function

BS Biochemistry

(2014-2015) Bioc 340 - Enzymology Lab

BS Biochemistry

Education
2006 - 2010: PhD

University of the Mediterranean
Microbiology and Biotechnology

2005 - 2006: Master 2

University of Claude Bernard
Structural and Functional Biochemistry

2004 - 2005: Master 1

Lebanese University
Biochemistry

Good

2001 - 2004: Bachelor

Lebanese University
Biochemistry

Good

2000 - 2001: Baccalaureate

Lady of Balamand High School
Life Sciences

Good

Conferences 1 participation

Publications 2 publications
Amal Najjar, Sylvie Robert, Clémence Guérin, Michèle Violet-Asther et Frédéric Carrière 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. Appl. Microbiol. Biotechnol. 2011

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.

Sylvie Fernandez, Amal Najjar, Sylvie Robert, Jean-David Rodier, Bruno Mahler, Frédéric Demarne, Frédéric Carrière et Vincent Jannin Specific assay of carboxyl ester hydrolase using PEG esters as substrate Anal. Methods 2010

The bile salt-stimulated lipase or carboxyl ester hydrolase (CEH) is a non-specific enzyme secreted by the exocrine pancreas and mammary glands. Recently we demonstrated that PEG esters were good substrates for CEH as it exhibited the highest specific activity ever recorded for this enzyme on PEG-8 monocaprylate. The aim of this study was to develop a specific and sensitive method for assaying CEH in biological samples in which several lipases are contained. Eight different PEG-n mono and dicaprylates with ethylene oxide units ranging from n = 6 to 32 were tested using the pH-stat technique. PEG-20 dicaprylate was the best substrate to discriminate CEH from other digestive lipases. Since pancreatic lipase related-protein 2 (PLRP2) was also found to display a significant activity on PEG-20 dicaprylate, experiments were designed to optimize the specificity of the assay for CEH. The main parameters for increasing CEH activity, while reducing that of PLRP2, were the pH and the concentration of bile salts. A linear relationship between the enzyme activity and the mass of CEH was established. The specificity of this assay was validated using gastrointestinal fluids containing CEH, PLRP2, gastric and pancreatic lipases.

Languages
English

Professional working proficiency

French

Full professional proficiency