title: An ancestral member of the polysaccharide lyase family 2 displays endolytic activity and magnesium dependence.
abstract: Polysaccharide lyases (PLs) are enzymes that cleave glycosidic linkages in hexuronate polysaccharides, such as homogalacturonan (HG), using a β-elimination mechanism. Traditionally, PL activities on HG have been associated with catalytic calcium cofactors, unusually high pH optima, and arginine Brønstead bases. Recently, however, PL families that harness transition metal cofactors, utilize lysine and histidine Brønstead bases, and display more neutral pH optima have been described. One such family is PL2, which has members found primarily in phytopathogenic (e.g., Dickeya spp. and Pectobacterium spp.) or enteropathogenic (e.g., Yersinia spp.) bacterial species. PL2 is divided into two major subfamilies that are correlated with either an endolytic or exolytic activity. This study has focused on the activity of a PL2 member, which is not classified within either subfamily and helps to illuminate the origin of enzyme activities within the family. In addition, the role of Mg(2+) as a preferential catalytic metal for an intracellular PL2 (PaePL2) is described. The implications for the relationship between catalytic metal selectivity and the cellular location of pectate lyase-mediated catalysis are discussed.
authors.affiliation: Lethbridge Research Station, Agriculture and Agri-Food Canada, 5403 1st Avenue South, Lethbridge, AB, T1J 4B1, Canada, wade.abbott@agr.gc.ca.
authors.forename: D Wade
authors.initials: DW
authors.lastname: Abbott
authors.forename: Dallas
authors.initials: D
authors.lastname: Thomas
authors.forename: Benjamin
authors.initials: B
authors.lastname: Pluvinage
authors.forename: Alisdair B
authors.initials: AB
authors.lastname: Boraston
mesh_terms: D000595:Amino Acid Sequence; D019143:Evolution, Molecular; D016680:Genome, Bacterial / Q000235:genetics; D008274:Magnesium / Q000378:metabolism*; D008969:Molecular Sequence Data; D056507:Paenibacillus / Q000201:enzymology* / Q000235:genetics; D011133:Polysaccharide-Lyases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid
chemical_list: D011133:Polysaccharide-Lyases; D008274:Magnesium