W0346

Distortion of Substrates in Class I and Class II Mannosidase Active Sites: A Structural Study. Niket Shah, Douglas A. Kuntz & David R. Rose, Dept. of Medical Biophysics, Univ. of Toronto, Ontario Cancer Institute, 610 University Avenue, Room 7-111, Toronto, ON M5G2M9 CANADA.

The N-glycosylation pathway is responsible for the covalent attachment of carbohydrate chains on asparagine residues of nascent proteins at Asn-X-Ser/Thr consensus sequences. These carbohydrate chains are thought to aid in cell signaling, immune recognition, and other processes.

Mannosidases are enzymes in the N-glycosylation pathway that cleave mannose linkages at different stages of the pathway. These enzymes fall into two broad classes (class I and class II) based on amino acid sequence, catalytic mechanism, and structure.

In recent years, crystal structures of mannosidases have been solved to high resolutions. For this study, we utilize two mannosidases for which crystal structures are available: endoplasmic reticulum α1,2-mannosidase from Saccharomyces cerevisiae (class I; abbreviated ERMI) and Golgi α-mannosidase II from Drosophila melanogaster (class II; abbreviated dGMII) (Vallée et al., 2000). Inhibitors against mannosidases are usually more efficacious against one class than another, as is expected with the divergent catalytic mechanisms.

We present the structural comparison of various carbohydrate analogs in the active sites of both ERMI and dGMII. It is hoped that the study of both strong and weak inhibitors will aid in the design of novel inhibitors against these and other enzymes of the N-glycosylation pathway.