| Popis: |
The naturally occurring polyamines play an essential role in cell growth and proliferation. The enzyme spermidine N8- acetyltransferase catalyzes the acetylation of spermidine utilizing acetyl-CoA as the acetyl donor. In this study, an in vitro acetyltransferase assay was used to determine the types of compounds which can inhibit this reaction. The enzyme was partially purified from rat liver nuclei and solubilized in 0.4 M KCl. The Km for spermidine was 0.47 mM. Studies on the nature of the active site indicated that: (i) a sulfhydryl group is essential for optimal activity as shown by inhibition with parahydroxymercuribenzoate and N -ethylmaleimide, (ii) a metal ion does not appear to be necessary for catalytic activity of this enzyme since EDTA, 2,2-dipryridil, and 1,10 phenanthroline were poor inhibitors of this enzyme, (iii) a lysine or another primary amine is likely to play a crucial role in this reaction since succinate anhydride and 2,4,6-trinitrobenzene sulfonic acid were effective inhibitors of this reaction and (iv) tyrosine is not likely present at the catalytic site since N -acetylimidazole produced no inhibition. |
