High-specificity affinity reagents for N-glycosylation site mapping and glycomics

DESCRIPTION: Glycans have several distinct properties that make them excellent targets for disease biomarkers. Firstly, the location of the glycans on the cell surface makes them the first point of contact of cellular interactions and thus crucial in thecontrol of normal metabolic processes. Cell surface molecules are also strategically exposed for surveillance by the immune system allowing for the potential of immune recognition of abnormal cells. Secondly, specific glycan structures that are not present, or are in low amounts, in normal states proliferate in disease states. And lastly, changes in glycosylation involve many proteins, including those that are highly abundant. Therefore, a single change in a cell's glycosylation machinery can affect many different glycoconjugates. To effectively employ and discover glycan disease markers new glycan-specific reagents are urgently needed. Using computational methods to guide molecular evolution, carbohydrate-processing enzymes will be converted into high affinity receptor proteins that retain the native specificity of the enzyme, but which no longer have enzyme activity. Because such a protein has lectin-like properties, but is derived from an enzyme, we are calling them Lectenz(r) . Lectenz(r) have severalpotential advantages over lectins and antibodies as glycomics reagents, including precise definition of specificity, ease of preparation in a monovalent form, and (for human homologues) minimal in vivo toxicity. In this proposal, the peptide N-glycanase F(PNGase F) carbohydrate-processing enzyme will be converted into a high-specificity affinity reagent for peptides and proteins that contain asparagine-linked carbohydrate chains. The Lectenz(r) based on PNGase F may be employed directly to address the needs of glycomics/proteomics analysis through sample enrichment, thus facilitating glycosylation site-mapping. Glycosylation site mapping is currently extremely tedious to perform and yet is essential in fully characterizing and exploiting glycans as markersof specific disease states. The principle advantages of an engineered Lectenz(r) are that the Lectenz(r) is specific to a defined carbohydrate sequence, and, in contrast to antibodies, will recognize that sequence in a broad range of glycan contexts. Further, in contrast to plant lectins, engineered Lectenz(r) are derived from enzymes that have exquisite substrate specificities and low toxicities. Lastly, as there is an abundance of carbohydrate- processing enzymes known, it is possible to employ the Lectenz(r) technology (patent pending) to assemble panels of affinity reagents tailor-made for characterizing, monitoring or detecting specific glycans. PUBLIC HEALTH RELEVANCE PUBLIC HEALTH RELEVANCE: We are converting carbohydrate-processing enzymes into high affinity receptor proteins (called Lectenz(r)) that can be used to help discover, detect and monitor glycan-based disease markers. The principle advantages of Lectenz(r) over other reagents, such as antibodies or plant lectins, is that they have known sequence specificity that is not context dependent, they may be produced as monomeric proteins, and for human homologues have minimal in vivo toxicity. Here a Lectenz(r) will be derived from the PNGase F carbohydrate-processing enzyme, for use asa high-specificity affinity reagent for peptides and proteins that contain asparagine-linked carbohydrate chains, which will find use in glycomics analyses aimed at disease marker discovery.