Structure of the Binding Site for Antithrombin

1- Ana.6S G-AM6s (where I = a-L-iduronic acid, Ana.6s 2-acetamido-2-deoxy-a-D-glucopyranose 6-sulfate, G = ) -D-glucuronic acid, and AMgs = 2,5-anhydro-D-mannitol 6-sulfate, the last arising from 2-deoxy- 

Similar, high-affinity fragments (of the size of dodeca- to tetradeca-saccharide), obtained by partial, deaminative cleavage of pig-mucosal heparin followed by affinity chromatography on antithrombin, contained, in addition to the tetrasaccharide sequence I-Ana,6s ( ANs.es least one trisulfated disaccharide unit, I2s ANs.es ( ) both sides of the 

6-di-C-sulfate. This atypical, trisulfated amino sugar was identified by (a) paper electrophoresis after alkaline cleavage of a nitrous acid-cleaved and periodate-oxidized, high-aflSnity octasaccharide, followed by nitrous acid deamination, and reduction with borohydride, and (b) n.m.r. spectroscopy.  

Structural variants in structure 11 appear compatible with high-aflSn-ity binding to antithrombin. Thus, the acetoxyl group of residue Ana,6s could be removed (by hydrazinolysis) and replaced by a sulfate group without loss of afifinity. Natural, high-aflSnity oligosaccharides con- 

Physically Separable Heparin Species Molecular Weight, and 

Because of a supposedly statistical cleavage of the biosynthetic precursor of heparin, and uneven distribution of incompletely transformed residues (see Sections II and VI), chains that constitute conventional heparin differ from each other, both in average length and in sulfation pattern. 

---