Erythrocytes desialylation

Desialylation of thrombocytes478 477 and erythrocytes also leads to their disappearance from circulation. Treatment of erythrocytes from different mammals, including man, with sialidase results in rapid clearance of these cells from the blood stream within a few hours, a phenomenon first observed by Perona and coworkers,478 and later investigated in various laboratories it was reviewed in Ref. 479. In man, the life-time of red blood-cells decreases from the normal 120 days to 2 h after sialidase treatment.4811... 

Complete desialylation of erythrocytes is not necessary for erythrocyte sequestration liberation of 15-20% of membrane sialic acids was found to be sufficient for a significant diminution of the life-time of erythrocytes.481,482 For an in vitro system with rat-peritoneal macrophages (see later), this threshold value was found to be only 10% when using soluble V. cholerae sialidase, but it was —30% when the erythrocytes were treated with the same enzyme immobilized on Sepharose.488... 

Incubation of sialyl substrates, such as a-1 acid glycoprotein, fetuin and sialyl lactose, with either live parasites or with preparations of lysed trypanosomes results in the release of sialic acid at an optimum pH of 6.0 to 6.5. Moreover, incubation of live trypomastigotes with human erythrocytes causes a time-dependent release of sialic acid from the erythrocyte surface. Similarly, the level of desialylation of erythrocytes from... 

C18H33NO15 503.456 Constit. of the desialylated portion of the glycan chains isol. from an alpha subunit of normal human chorionic gonadotropin (hCG). Constit. of sialoglycopeptides from human 0-MN-type erythrocytes. 

Erythrocyte Glycoproteins.—A glycoprotein from human blood-group O erythrocytes could be desialylated by hydrolysis in 0.025M-sulphuric acid at 60°C. ... 

Erythrocyte-membrane Glycoproteins.—Human erythrocyte-membrane glycoprotein has been modified to a tryptic glycopeptide, which was desialylized by mild acid treatment. The non-reducing, terminal D-galactosyl residue of the glycopeptide was labelled by enzymic oxidation and reduction with sodium borotritide. 

This phenomenon seems to apply to circulating cells as well. In addition to the aforementioned studies with lymphocytes, Gattegno et al. (1974) found that desialylated erythrocytes are also rapidly removed from the circulation. Based upon these observations, Rogers and Korn-... 

The aforementioned considerations suggest a function for the sialidase found associated with the plasma membranes of liver cells (Schengrund et al.y 1972 Visser and Emmelot, 1973) to desialylate circulating sialoglycoproteins for their subsequent uptake by the hepatocytes. The sialidase of erythrocyte membranes (Bosmann, 1974) may function in determining their half-life in the circulation. 

---