Biological roles of glycans

Abstract

Simple and complex carbohydrates (glycans) have long been known to play major metabolic, structural and physical roles in biological systems. Targeted microbial binding to host glycans has also been studied for decades. But such biological roles can only explain some of the remarkable complexity and organismal diversity of glycans in nature. Reviewing the subject about two decades ago, one could find very few clear-cut instances of glycan-recognition-specific biological roles of glycans that were of intrinsic value to the organism expressing them. In striking contrast there is now a profusion of examples, such that this updated review cannot be comprehensive. Instead, a historical overview is presented, broad principles outlined and a few examples cited, representing diverse types of roles, mediated by various glycan classes, in different evolutionary lineages. What remains unchanged is the fact that while all theories regarding biological roles of glycans are supported by compelling evidence, exceptions to each can be found. In retrospect, this is not surprising. Complex and diverse glycans appear to be ubiquitous to all cells in nature, and essential to all life forms. Thus, >3 billion years of evolution consistently generated organisms that use these molecules for many key biological roles, even while sometimes coopting them for minor functions. In this respect, glycans are no different from other major macromolecular building blocks of life (nucleic acids, proteins and lipids), simply more rapidly evolving and complex. It is time for the diverse functional roles of glycans to be fully incorporated into the mainstream of biological sciences.

Conotoxins: Structure, Therapeutic Potential and Pharmacological Applications

“…Although, the role of PTMs in conopeptides remain mostly unexplored. In general, the PTMs of amino acids extends the range of biological functions of the protein; for example, glycosylation helps in providing structural components, modifying physiological properties, mediating & modulating cell-adhesion and signaling [30,31]. In case of conotoxins, the PTMs of amino acids increase the toxin potency [24,25,32,33] and stabilize the three-dimensional structure of the peptide [34][35][36].…”

Restricted processing of CD16a/Fc γ receptor IIIa N-glycans from primary human NK cells impacts structure and function

“…More highly processed N-glycans may also include hybrid forms and the predominant complex-types found on cell surfaces and circulatory serum proteins. Additional to folding, N-glycans promote secretion, protection against proteolysis, reduce antigenicity, extended serum half-life, and contribute specific epitopes for receptor binding as well as impact protein structure and function (14)(15)(16).…”

Predicting glycosaminoglycan surface protein interactions and implications for studying axonal growth

“…lycans and proteins are important partners in the regulation of fundamental biological processes such as the immune response, signal transduction, development, and pathogen invasion (1). An understanding of the wide array of glycan-protein interactions is critical to mapping the biological functions of glycans and will pave the way for the development of new therapies that target glycan-protein interactions that contribute to diseases such as cancer and autoimmune and neurodegenerative disorders (2).…”