An NMR and Molecular Modeling Study of the Site-Specific Binding of Histamine by Heparin, Chemically Modified Heparin, and Heparin-Derived Oligosaccharides

Abstract

The diprotonated form of histamine binds site-specifically to heparin, a highly sulfated 1-->4 linked repeating copolymer comprised predominantly of 2-O-sulfo-alpha-L-iduronic acid (the I ring) and 2-deoxy-2-sulfamido-6-O-sulfo-alpha-D-glucopyranosyl (the A ring). The binding is mediated by electrostatic interactions. The structural features of histamine and heparin, which are required for the site-specific binding, have been identified from the results of (1)H NMR studies of the binding of histamine by six heparin-derived oligosaccharides and four chemically modified heparins and molecular modeling studies. The results indicate that the imidazolium ring of diprotonated histamine is critical for directing site-specific binding, while the ammonium group increases the binding affinity. The imidazolium ring binds within a cleft, with the A ring of an IAI triad at the top of the cleft, and the I rings forming the two sides. The H3 proton of the A ring is in the shielding cone of the imidazolium ring. The carboxylate group of the I-ring at the reducing end of the IAI triad and possibly the sulfamido group of the A-ring are essential for site-specific binding, whereas the 2-O-sulfate group of the I ring and the 6-O-sulfate group of the A ring are not. The results indicate that histamine binds to the IAI triad with the I rings in the (1)C(4) conformation. Also, the configuration of the carboxylate group is critical, as indicated by the absence of site-specific binding of histamine by the related IAG sequence, where G is alpha-D-glucuronic acid. The molecular modeling results indicate that the N1H and N3H protons of the imidazolium ring of site-specifically bound histamine are hydrogen bonded to the carboxylates of the I rings at the nonreducing and reducing ends of the IAI trisaccharide sequence.

Structural Recognition by Recombinant Human Heparanase That Plays Critical Roles in Tumor Metastasis

“…The elucidated sequence requirement was in good agreement with the cleavage sequence, suggested based on the structures of the remnant cleavage sites found in the penta-and trisaccharides isolated from porcine intestinal native Hep-GAG after digestion with bacterial heparinase/heparitinases (36,40,53). Among a series of sulfated oligosaccharides generated by bacterial lyases (45), the unsaturated pentasaccharide, 36), are of particular interest in view of the recognition sequence by porcine or mammalian heparanase.…”

“…The GlcN 3-O-sulfate structure, which is enclosed in the rectangle, causes inhibition of the enzyme in principle, although it also has promoting effects through its negative charge. C, the putative octasaccharide recognition sequence by the human heparanase in native Hep chains deduced from the results obtained by the heparanase digestion experiments of structurally defined oligosaccharides in the present study and the mono-and oligosaccharides previously isolated by bacterial heparinase/heparitinase digestions of porcine intestinal Hep (36,40,53) and bovine lung and intestinal Hep (54). recombinant iduronate-2-O-sulfatase 2 (see also Ref.…”

“…The above mentioned oligosaccharides were most likely generated from the sequence of -HexUA(2S)-GlcN(NS,6S)-IdoUA-GlcNAc(6S)-GlcUA*-GlcN(NS)-Ido-UA(2S)-GlcN(NS,6S)-by the action of endogenous heparanase on the glucuronidic bond indicated by an asterisk. Although the unsaturated pentasaccharide is a major digestion product (40,53), the above mentioned trisaccharide was a minor product. In this context, it is noteworthy that Nader et al (54) identified free GlcN(NS,6S) as one of the major products among other unsaturated di-and tetrasaccharides in the Flavobacterium heparinum haparinase digest of bovine lung and intestine Hep preparations.…”

Pharmacology of Heparin and Related Drugs

“…Heparin is found naturally in mast cell granules, where it interacts with histamine; this interaction has been analyzed in some structural detail and is highly ordered and specific, with the imidazolium ring of protonated histamine located between two IdoA2S residues by hydrogen bonds between the histamine NH and IdoA carboxylates (Chuang et al, 2000). Histamine alters the profile of oligosaccharides resulting from depolymerization with heparinase I (Chuang et al, 2001(Chuang et al, , 2002.…”

Serotonin content is elevated in the immune cells of histidine decarboxylase gene knock-out (HDCKO) mice. Focus on mast cells

“…In the present experiments the reduction of mast cell number in the peritoneal fluid was pronounced (according to Wiener et al [18] this is a 75-80 % reduction) and the increase in serotonin content was prominent. We don't know whether this is a compensation for the loss of histamine or indicates a requirement for heparin which binds the biogenic amines in the granule [21,22], subsequent to the imbalance in heparin-histamine-serotonin-basic protein normal complex. The biogenic amines are the primary components of the mast cell granules, though heparin is indispensable for their composition [23].…”