CHARACTERIZATION OF S-ADENOSYLMETHIONINE DECARBOXYLASE INDUCED BY HUMAN CYTOMEGALOVIRUS-INFECTION

Infection of human diploid embryonic lung (MRCS) cells by human cytome galovirus (HCMV), strain AD169, increased the activity of a key enzyme in the synthesis of polyamines: S-adenosylmethionine decarboxylase (E .C. 4.1.1.50). The initial peak of S-adenosylmethionine decarboxylase activity occurred about 15 h postinfection. S-Adenosylmethionine decar boxylase was purified using a highly specific affinity chromatography step from HCMV-infected and control uninfected MRC5 cells. No differen ce was found between the two enzymes in their stability to heat or eff ect of pH on activity. Both enzymes were activated only by putrescine. The appK(m) for S-adenosylmethionine for the virus-induced enzyme was 1.7 times higher than the appK(m) for the control enzyme. The most dr amatic difference observed was in the effect of high salt concentratio n on enzyme activity. S-Adenosylmethionine decarboxylase from HCMV-inf ected cells was unaffected by 0.8 M NaCl, whereas the enzyme from unin fected cells was inhibited by 50% at 0.45 M NaCl and was significantly inhibited at a concentration of 0.8 M NaCl. Thus, different forms of S-adenosylmethionine decarboxylase probably exist in infected and unin fected MRCS cells.