Carbohydrates located on the top of the “cap” contribute to the adhesive and enzymatic functions of vascular adhesion protein‐1

Vascular adhesion protein 1 (VAP‐1) is an endothelial adhesion molecule with an enzymatic activity. It deaminates biogenic amines, resulting in the formation of aldehydes and hydrogen peroxide. During the enzymatic reaction a transient Schiff base is formed between endothelial VAP‐1 and its leukocytic ligand, and this interaction is important for lymphocyte adhesion. VAP‐1 monomer has six potential N‐linked, and three putative O‐linked glycosylation sites and an SSSS sequence potentially forming an attachment site for an adjacent O‐linked site. In this work we modeled the carbohydrate decorations on a structural model of VAP‐1, and studied which of those potential glycosylation sites are utilized, and whether those decorations accessible to a lymphocyte ligand are important in lymphocyte adhesion and enzymatic activity of VAP‐1. We show that, unlike the O‐linked attachment sites, all six N‐linked glycosylation sites are in use. Furthermore, mutation of the N‐linked attachment sites strategically located on the top of the molecule reduces lymphocyte adhesion in non‐static conditions, and enhances the catalytic activity of membrane‐bound human VAP‐1 in static conditions, suggesting that glycosylation regulates the functional properties of VAP‐1.