S-ADENOSYL-L-METHIONINE DECARBOXYLASE OF ACANTHAMOEBA-CASTELLANII (NEFF) - PURIFICATION AND PROPERTIES

S-Adenosyl-L-methionine decarboxylase (AdoMetDC) has been purified to near homogeneity from the Neff strain of Acanthamoeba castellanii. The holoenzyme molecular mass is 88.8 kDa, including two copies each of a 32.8 kDa alpha-subunit and a 10-15 kDa beta-subunit. The alpha-subunit contains the active site. It has an N-terminal pyruvoyl group, and the first 19 amino acids are 63 and 74% identical with comparable sequences from yeast and mammals, respectively. The apparent K(m) for S-adenosylmethionine (AdoMet) in the presence of 2 mM putrescine was 30.0 muM. The enzyme was stimulated 2-fold by putrescine, but was unaffected by spermidine. It was inhibited by the following anti-metabolites, listed with their K1 values: Berenil (0.17 muM), pentamidine (19.4 muM), propamidine (334 muM), hydroxystilbamidine (357 muM), methylglyoxal bis(guanyl-hydrazone) (604 muM) and ethidium bromide (1.3 mM). Activity of the enzyme fell to undetectable levels during cell differentiation (encystment).