Akademik Veri Yönetim Sistemi
Bioscience Reports, cilt.24, sa.1, ss.41-53, 2004 (SCI-Expanded)
Erythrocytes from cancer patients exhibited up to fivefold higher NAD glycohydrolase activities than control erythrocytes from normal subjects and also similarly increased [ 14C] ADP-ribose uptake values. When [adenosine- 14C] NAD was used instead of free [ 14C] ADP-ribose, the uptake was dependent on ecto-NAD glycohydrolase activity. This was reflected in the inhibition of ADP-ribose uptake from [adenosine- 14C] NAD by Cibacron Blue. ADP-ribose uptake in erythrocytes appeared to be complex: upon incubation with free [ 14C] ADP-ribose, the radiolabel associated with erythrocytes was located in nearly equal parts in cytoplasm and plasma membrane. Part of [ 14C] ADP-ribose binding to the membrane was covalent, as indicated by its resistance to trichloroacetic acid-treatment. A preincubation with unlabeled ADP-ribose depressed subsequent erythrocyte NAD glycohydrolase activity and binding of [ 14C] ADP-ribose to erythrocyte membrane; but it failed to inhibit the transfer of labeled ADP-ribose to erythrocyte cytoplasm. On the other hand, incubation with [adenosine- 14C] NAD did not result in a similar covalent binding of radiolabel to erythrocyte membrane. In line with this finding, a preincubation with unlabeled NAD was not inhibitory on subsequent NAD glycohydrolase reaction and ADP-ribose binding. ADP-ribose binding and NAD glycohydrolase activities were found also in solubilized erythrocyte membrane proteins and, after size fractionation, mainly in a protein fraction of around 45kDa-molecular weight.