Glyco@Seminar: Miroslaw Cygler

on the October 26, 2018

October 26th, 11:00am
Miroslaw Cygler from University of Saskatchewan (Saskatoon, Canada), will give a talk about " The structures and catalytic mechanisms of ulvan lyases from three PL families ".

Miroslaw Cygler and ThirumalaiSelvi Ulaganathan, Department of Biochemistry, Microbiology and Immunology, University of Saskatchewan, Saskatoon, SK, Canada

Ulvan is a complex sulfated polysaccharide biosynthesized by marine green algae from genus Ulva and Enteromorpha and constitutes one of the two major polysaccharides of their cell wall. This polysaccharide is composed predominantly of 3-sulfated rhamnose (R3S), glucuronic acid (GlcA), iduronic acid (IdoA) and xylose. Several bacterial species isolated from marine environment were shown recently to produce enzymes capable of degrading ulvan. Among them are Nonlabens ulvanivorans, Alteromonas and Pseudoalteromonas. The ulvan degrading lyases are presently classified into three families in the CAZy database, namely PL24, PL25 and PL28.

We have determined the structures and characterized catalytic mechanisms of representative lyases from all three of these families. They adopt folds that have been previously observed in among the PL lyase families and appear to follow the Tyr/His general catalytic mechanism. These enzymes cleave the glycosidic bond between 3-sulfated rhamnose (R3S) and uronic acid  via a ß-elimination mechanism. The active site and substrate binding residues have been identified and confirmed by mutagenesis.

Published on October 22, 2018

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