Impaired amylase activities caused by binding of abnormal immunoglobulin A in patients with macroamylasemia.
Eight of thirty analyzed samples of immunoglobulin A-linked macroamylases showed significantly higher enzyme activity with the low molecular (short-chain amylose) substrate than with the macromolecular (blue starch polymer) substrate. Immunoglobulin A, which had been separated from one macroamylase, was found to bind to normal amylases from different organs resulting in decreased affinity for the macromolecular substrate. These findings suggest that abnormal immunoglobulin A is stoichiometrically associated with a specific site adjacent to the active site of the amylase molecule. In addition, alpha-amylase inhibitor failed to inhibit the enzyme activity of some macroamylases with macromolecular substrate, suggesting that immunoglobulin A blocked the binding site for the inhibitor. We conclude that immunoglobulin A-linked macroamylases have heterogeneous binding sites for immunoglobulin A, resulting in functional abnormality of amylase activity.
K
K
Adachi
K
K
Suzuki
Y
Y
Ohno
B
B
Sato
D000681:Amylases / Q000037:antagonists & inhibitors / Q000097:blood*; D001665:Binding Sites; D002850:Chromatography, Gel; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007070:Immunoglobulin A / Q000378:metabolism*; D066298:In Vitro Techniques
D007070:Immunoglobulin A; D000681:Amylases; C001663:macroamylase