Heparan Sulfate Domains Required for Fibroblast Growth Factor 1 and 2 Signaling through Fibroblast Growth Factor Receptor 1c.

A small library of well defined heparan sulfate (HS) polysaccharides was chemoenzymatically synthesized and used for a detailed structure-activity study of fibroblast growth factor (FGF) 1 and FGF2 signaling through FGF receptor (FGFR) 1c. The HS polysaccharide tested contained both undersulfated (NA) domains and highly sulfated (NS) domains as well as very well defined non-reducing termini. This study examines differences in the HS selectivity of the positive canyons of the FGF12-FGFR1c2 and FGF22-FGFR1c2 HS binding sites of the symmetric FGF2-FGFR2-HS2 signal transduction complex. The results suggest that FGF12-FGFR1c2 binding site prefers a longer NS domain at the non-reducing terminus than FGF22-FGFR1c2 In addition, FGF22-FGFR1c2 can tolerate an HS chain having an N-acetylglucosamine residue at its non-reducing end. These results clearly demonstrate the different specificity of FGF12-FGFR1c2 and FGF22-FGFR1c2 for well defined HS structures and suggest that it is now possible to chemoenzymatically synthesize precise HS polysaccharides that can selectively mediate growth factor signaling. These HS polysaccharides might be useful in both understanding and controlling the growth, proliferation, and differentiation of cells in stem cell therapies, wound healing, and the treatment of cancer.

Combinatorial one-pot chemoenzymatic synthesis of heparin.

Contamination in heparin batches during early 2008 has resulted in a significant effort to develop a safer bioengineered heparin using bacterial capsular polysaccharide heparosan and recombinant enzymes derived from the heparin/heparan sulfate biosynthetic pathway. This requires controlled chemical N-deacetylation/N-sulfonation of heparosan followed by epimerization of most of its glucuronic acid residues to iduronic acid and O-sulfation of the C2 position of iduronic acid and the C3 and C6 positions of the glucosamine residues. A combinatorial study of multi-enzyme, one-pot, in vitro biocatalytic synthesis, carried out in tandem with sensitive analytical techniques, reveals controlled structural changes leading to heparin products similar to animal-derived heparin active pharmaceutical ingredients. Liquid chromatography-mass spectrometry and nuclear magnetic resonance spectroscopy analysis confirms an abundance of heparin's characteristic trisulfated disaccharide, as well as 3-O-sulfo containing residues critical for heparin binding to antithrombin III and its anticoagulant activity. The bioengineered heparins prepared using this simplified one-pot chemoenzymatic synthesis also show in vitro anticoagulant activity.