[Relationship between the structure and activity of a histamine-blocking serum glycoprotein]

A plasmatic glycoprotein is submitted to a mild periodate oxydation and its pharmacological activity is studied. This glycoprotein contains much N acetyl Neuraminic Acid (NANA = 15 p. cent), and it reduces the biological activity of histamine on smooth muscle such as guinea pig ileum. See article. We also identify the 8 NANA and 7 NANA derivaties. Th only 8 carbon derivative is obtained when about one mole of m-periodate is consumed for one mole of NANA. The 7 carbon derivative appears as soon as the consumption of a second mole leads ta a second cleavage. These results prove that the oxydation islimited to the sole N acetyl neuraminic acid and more precisely to the lateral polyhydroxylic chain. Under these conditions, pharmacological activity gradually decreases, it disappears as soon as the lateral polyhydroxylic chain is completely cut off.