THE LINKAGE OF THE AMINO GROUP IN HEPARIN

Abstract

Alleged Acetyl Content of Heparin Many erroneous assumptions have been made from time to time as to the chemical nature and the composition of heparin.To these we must now add the assumption (l-6) that heparin contains an acetyl group, which at one time seemed fairly well justified.As pointed out by Fiirth and coworkers (7), the amino sugar is monoacetylated in all the known mucopolysaccharides and in chitin.Thus, acetic acid occurs in chondroitinsulfuric acid (8), in the hyaluronic acid of Meyer (3), in the immunopolysaccharide of type I pneumococci (9), and in the blood group substances (10,11).The first analytical findings on heparin also supported this view.The analytical methods applied, however, soon proved somewhat unreliable.The Kuhn-Roth (12) alkaline hydrolysis in methyl alcohol, applied in the first communication (l), later proved, when applied to chondroitinsulfuric acid (2), to liberate a large excess of acid, as found simultaneously by Friedrich and Sternberg (13).When, on the contrary, the toluenesulfonic acid was used for hydrolysis, either as recommended by Friedrich and Rapoport ( 14) or as modified by Friedrich and Sternberg, no acetic acid whatsoever was found in lieparin.Taking into account the extreme slowness with which reducing groups are liberated on acid hydrolysis of heparin, Jorpes and BergstrGm, who unfortunately did not follow the liberation of the amino group quantitatively, thought that strong hydrolytic agents were necessary, such as 10 per cent (by volume) of sulfuric acid.In fact, acetic acid was also identified by them as silver salt in the distillate after acid hydrolysis.In the meantime a negative finding was made by Masamune, Suzuki, and Kondoh (15) and by Wolfrom and coworkers ( 16).The latter authors applied both the toluenesulfonic acid method and the chromic acid oxidation method for the determination of the CH& group.The findings of the Japanese workers and of Wolfrom and coworkers necessitated a reinvestigation of the question with more reliable methods.