Ghazal KHALED PhD defense

Organic Chemistry & Interfaces (COrInt) team

Abstract
Glycosyltransferases (GTs) are enzymes involved in the synthesis of glycoconjugates and polysaccharides, molecules with a wide range of biological activities and thus they are attractive for biotechnological applications. This project focuses on a novel processive and transmembrane GT from the archaea Pyroccous horikoshii referred to as Pho-GT2, classified into the GT2 family, according to the CAZy database. A phylogenetic analysis including characterized GT2 revealed that Pho-GT2 forms a distinct clade with other protein from thermococcales and shares a common evolutionary ancestor with chitin, poly N-acetyl glucosamine and hyaluronan synthases. In silico studies were done in order to indentify potential substrates through structural alignments and docking. A recombinant strain was designed to produce a truncated form of the enzyme called Pho-GT2𝚫C without the transmembrane domains in order to study its enzymatic activity in vitro. Pho-GT2𝚫C showed a versatile hydrolytic activity toward five UDP-sugars, but no transfer reaction was observed. The full length Pho-GT2 was also expressed in order to isolate tranfer product. Several procedures were applied to characterize these products. NMR analysis revealed novel saccharides, which were fully hydrolyzed by a hyaluronidase. This study provide insights into the mechanism of a new GT class with a yet unidentified actitvity.

Jury
Président : Alain DUFOUR, Professeur des universités, LBCM, Université de Bretagne Sud
Examinateur : Adrienne KISH , Maître de conférences , Muséum National d’histoire naturelle
Examinateur : Nathalie KHREICH , Professeur, Université Libanaise
Rapporteur : Mirjam CZJZEK, Directrice de recherche CNRS, Station biologique de Roscoff
Rapporteur : Christine DELBARRE-LADRAT, Chargée de recherche, Ifremer, Nantes
Co-Directeur de thèse : Thierry BENVEGNU, Professeur, ENSCR, ISCR, Université de Rennes
Co-Directeur de thèse : Sylvain TRANCHIMAND , Maître de conférences, ENSCR, ISCR, Université de Rennes
Co-Directeur de thèse (Liban): Hala CHAMIEH, Professeur, Université Libanaise

Contacts
Thierry Benvegnu, [email protected]
Sylvain Tranchimand, [email protected]