[Release from human alpha 2-macroglobulin of a peptide inhibitor of G1-S transition of hepatocytes in vivo. Role of trypsin, thrombin and various chemical agents].
Inhibitory effect on the G1-S transition of hepatocytes in vivo was measured in the ultrafiltrates of alpha 2 M/trypsin and alpha 2 M/thrombin complexes (alpha 2 macroglobulin: alpha 2 M). Untreated human alpha 2 M activity corresponds to one inhibitory unit/mg. When alpha 2 M/trypsin and alpha 2 M/thrombin complexes were ultrafiltrated at pH 7.8 on PM 10 Amicon membrane, 300 inhibitory units were obtained from 1 mg of alpha 2 M. After treatment at pH 10 of the same complexes, 30,000 inhibitory units were obtained from the same quantity of alpha 2 M. Such a high activity was observed when native alpha 2 M was used before alpha 2 M/enzyme interaction. When alpha 2 M was previously treated by an aliphatic amine or reduced and alkylated, the activity found in ultrafiltrates was very low. In the same way, a low activity was observed when the captation capacity of alpha 2 M was exceeded. These results show that specific cleavages on alpha 2 M molecule are needed to obtain a large amount of active inhibitory peptide.
D002453:Cell Cycle / Q000187:drug effects; D006020:Glycopeptides / Q000302:isolation & purification* / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D008099:Liver / Q000166:cytology* / Q000187:drug effects; D013917:Thrombin / Q000494:pharmacology*; D014357:Trypsin / Q000494:pharmacology*; D014462:Ultrafiltration; D000511:alpha-Macroglobulins / Q000032:analysis*
D006020:Glycopeptides; D000511:alpha-Macroglobulins; D014357:Trypsin; D013917:Thrombin
Libération à partir de l'alpha 2 macroglobuline humaine d'un peptide inhibiteur de la transition G1-S des hépatocytes in vivo. Rôle de la trypsine, de la thrombine et de divers agents chimiques.