Exploring marine glycans: structure, function, and the frontier of chemical synthesis

Abstract

Marine glycans are structurally diverse biomolecules that play pivotal roles in oceanic carbon cycling by regulating microbial metabolism, accelerating organic matter turnover, and contribute to carbon sequestration. Glycans originating from marine organisms exhibit a wide range of bioactivities and applications in medicine, biotechnology, cosmetics, food and agriculture. The structural complexity of glycans poses significant challenges in understanding their functions, as traditional purification and characterization methods are often hindered by their inherent heterogeneity. To overcome these challenges, enzymatic extraction using glycoside hydrolases and carbohydrate-active enzymes (CAZymes) enables the selective recovery of native glycans, while automated glycan assembly (AGA) provides a robust approach for the rapid and reproducible synthesis of structurally defined glycans. Subjecting synthetic glycans to enzymatic degradation enables researchers to explore the inverse relationship between glycan complexity and microbial degradation, suggesting that algae can generate complex glycans at a rate exceeding bacterial decomposition, thereby reinforcing carbon storage. Here, we present a comprehensive overview of marine glycan sources and their structural diversity. We highlight the importance of employing two complementary methods, enzymatic extraction as a critical tool for glycan identification and AGA as an advanced synthetic platform, to build a refined framework for elucidating the ecological role and industrial potential of marine glycans.

Fig. 1. Overview over marine glycans and methods to establish their structure–activity relationships. (A) Marine glycans, sources, and applications. (B) Glycans as central metabolic fuels in the marine carbon cycle. (C) Enzymatic extraction and automated glycan assembly as complementary methods to access marine glycans.

Fig. 2. Structures of marine glycans derived from macroalgae. Chemical motifs highlight core structural features specific to each glycan, while the representative structures illustrate the diversity of these glycans in nature. All glycan symbols follow the symbol nomenclature for glycans (SNFG) guidelines.

Fig. 3. Structures of marine glycans derived from marine invertebrates, vertebrates, and microorganisms. Chemical motifs highlight core structural features specific to each glycan, while the representative structures illustrate the diversity of these glycans in nature. All glycan symbols follow the symbol nomenclature for glycans (SNFG) guidelines.

Fig. 4. Challenges in marine glycan biodegradation by enzymes.

Fig. 5. Scope of AGA in marine glycan synthesis.

Sandhya Mardhekar

Phuong Luong

Peter H. Seeberger