Evolution of glycosaminoglycans: Comparative biochemical study

Abstract

Glycosaminoglycans, a major component of the extracellular matrix molecules in animal tissues, play important roles in various physiological events. Glycosaminoglycans are found in not only vertebrates but also many invertebrates, implying a conserved function in the animal kingdom. Here, we discuss the analysis of glycosaminoglycans in 11 invertebrate phyla focusing on structure as well as physiological functions elucidated in model organisms. Various sulfated structures of heparan sulfate are widely distributed from very primitive organisms to humans, indicating an involvement in fundamental biological processes. By contrast, chondroitin/dermatan sulfate from lower organisms is limited in its structural complexity and often associated with a particular function. The presence of hyaluronic acid outside of vertebrates has been reported only in a mollusk.

Keywords: chondroitin sulfate; dermatan sulfate; evolution; glycosaminoglycan; heparan sulfate; hyaluronic acid; invertebrate.

Figure 1

The backbone structure of GAGs. CS or DS is composed of alternating disaccharide units of GlcA or IdoA and GalNAc, respectively. R₁, R₂, R₃, R₄ = −H or −SO₃H. Modification with β-D-glucose at the R₂ position has been found in squid CS. The presence of the α-L-fucose branch at the R₄ position has been reported in the CS preparations from sea cucumber and king crab. HS is composed of alternating disaccharide units of GlcA or IdoA and GlcN. R₁ = −COCH₃ or −SO₃H; R₂, R₃, R₄, R₅ = −H or −SO₃H. Recently, sulfation at the R₅ position was discovered in a bivalve HS. HA is a linear polymer composed of GlcA and GlcNAc.

Figure 2

Distribution of GAGs in the animal kingdom.