Structural Studies of Pectate Degrading Enzymes

University Of Missouri-Kansas City, Columbia MO

Investigators

Abstract

Yoder MCB 9983108 The goal of this research is to determine the three-dimensional structures of the pectate degrading enzymes, using X-ray crystallography. The work will focus on bacterial forms of the enzymes, from the phytopathogenic Ralsonia solanacearum, Erwinia carotovora, and Erwinia chrysanthemi. To obtain the details of the structures of specific residues, both catalytic and substrate binding, the structure determination of several additional polygalacturonases, pectate lyases, and pectin lyases will be carried out. Pectate degrading enzymes have significant roles in agriculture, as well as industry. The microbial forms of the enzymes are virulence factors in plant diseases associated with plant tissue maceration. Plant polygalacturonases are involved in plant growth and fruit ripening. Fungal polygalacturonases are widely used in the food and beverage industry, particularly in juice preparation. Polygalacturonase and pectate lyase bind the same saccharide polymer, but cleave the glycosidic bond by different enzymatic mechanisms. In contrast, pectin lyase binds to a methyl-esterified form of the saccharide polymer, but cleaves the glycosidic bond by a similar mechanism as pectate lyase. These enzymes provide a convenient system to probe structural differences between hydrolytic (polygalacturonase) and b-elimination (pectate and pectin lyase) cleavage of glycosidic bonds. The abundance of isoforms of these enzymes allows a structural comparison to elucidate differences in enzymatic rates and differences in the degree of polymerization of the oligogalacturonide endproducts.