Contribution of chemical 6-O-sulfation of the aminodeoxyhexose residues in whale heparin with high affinity for antithrombin III to its anticoagulant properties

Deiminated proteins and extracellular vesicles - Novel serum biomarkers in whales and orca

Peptidylarginine deiminases (PADs) are a family of phylogenetically conserved calcium-dependent enzymes which cause post-translational protein deimination. This can result in neoepitope generation, affect gene regulation and allow for protein moonlighting via functional and structural changes in target proteins. Extracellular vesicles (EVs) carry cargo proteins and genetic material and are released from cells as part of cellular communication. EVs are found in most body fluids where they can be useful biomarkers for assessment of health status. Here, serum-derived EVs were profiled, and post-translationally deiminated proteins and EV-related microRNAs are described in 5 ceataceans: minke whale, fin whale, humpback whale, Cuvier's beaked whale and orca. EV-serum profiles were assessed by transmission electron microscopy and nanoparticle tracking analysis. EV profiles varied between the 5 species and were identified to contain deiminated proteins and selected key inflammatory and metabolic microRNAs. A range of proteins, critical for immune responses and metabolism were identified to be deiminated in cetacean sera, with some shared KEGG pathways of deiminated proteins relating to immunity and physiology, while some KEGG pathways were species-specific. This is the first study to characterise and profile EVs and to report deiminated proteins and putative effects of protein-protein interaction networks via such post-translationald deimination in cetaceans, revealing key immune and metabolic factors to undergo this post-translational modification. Deiminated proteins and EVs profiles may possibly be developed as new biomarkers for assessing health status of sea mammals.

Characterization and mutagenesis of Gal/GlcNAc-6-O-sulfotransferases

The installation of sulfate groups on the carbohydrate residues of glycoproteins, glycolipids, and glycosaminoglycans is a critical posttranslational modification that occurs in all higher eukaryotes. The Gal/GalNAc/GlcNAc-6-O-sulfotransferases (GSTs) are a recently discovered family of carbohydrate sulfotransferases that share significant sequence homology at the amino acid level and mediate a number of different biological processes such as leukocyte adhesion at sites of chronic inflammation. Structural and mechanistic studies of this family of sulfotransferases have been hindered by the lack of a productive recombinant protein expression system. We developed a baculovirus expression system for five of the seven cloned GSTs and determined their kinetic parameters using both thin-layer chromatography and a recently developed polymer dot-blot assay. We used these tools to perform the first site-directed mutagenesis study of a member of this sulfotransferase family, GST2. Using sequence alignments with other carbohydrate and cytosolic sulfotransferases, we selected residues within the putative binding regions for 3'-phosphoadenosine 5'-phosphosulfate (PAPS) and the carbohydrate substrate for mutagenesis. Kinetic analysis of the mutants identified residues that are essential for catalytic activity. These results should facilitate mechanistic studies and the development of small molecule inhibitors of this enzyme family to ameliorate chronic inflammatory diseases.

Chemical change involved in the oxidative-reductive depolymerization of heparin

A solution of hog intestinal heparin (average M(r) 12,000, anti-clotting activity 168 USP units/mg) in 0.2 M phosphate buffer (pH 7.2), was incubated in the presence of Fe2+ for 20 h at 50 degrees under an O2 atmosphere to yield oxidative-reductively depolymerized heparin (ORD heparin, average M(r) 3,000, anti-clotting activity 34 USP units/mg). Chemical analysis of the ORD heparin showed a 22, 26, and 14% loss of hexosamine, uronic acid, and N-acetyl group, respectively, but no remarkable loss of both total and N-sulfate groups. 1H and 13C NMR spectroscopic analysis indicated no decrease in the amount of L-iduronic acid 2-sulfate, but a marked loss of nonsulfated uronic acid (73 and 39% loss of D-glucuronic acid and L-iduronic acids, respectively, the sum of which corresponds to the chemically determined loss of total uronic acid). The results indicated that the ORD reaction of heparin proceeds essentially by destruction of monosaccharide units, except L-iduronic acid 2-sulfate residues, due to oxygen-derived free radicals, followed by secondary hydrolytic cleavage of the resulting unstable residues.

Anticoagulant and antithrombin activities of oversulfated fucans

Three species of oversulfated fucans having different sulfate contents (the ratio of sulfate/total sugar residues, 1.38-1.98) were prepared by chemical sulfation of a fucan sulfate (sulfate/sugar ratio, 1.28) isolated from the brown seaweed Ecklonia kurome. The anticoagulant activities of the oversulfated fucans were compared with that of a parent fucan with respect to activated partial thromboplastin time (APTT) and thrombin time (TT) in plasma. The respective activities (for APTT and TT) of the oversulfated fucans increased to 110-119% and 108-140% of the original values with increase in their sulfate content. The anticoagulant activity with respect to APTT (173 units/mg) of an oversulfated fucan (sulfate/sugar ratio, 1.98) was higher than that (167 units/mg) of heparin used as a standard. The heparin cofactor II-mediated antithrombin activity of the oversulfated fucans also increased significantly with increase in sulfate content. The maximum activity was higher than those of the parent fucan and heparin. However, the increment of the anticoagulant and the antithrombin effects gradually decreased with increase in the sulfate content of the fucans. These results indicate that the effects of the fucan sulfate are dependent on its sulfate content until a plateau is reached.