Ornithine decarboxylase activity in uninfected and vaccinia virus-infected hela cells

Summary Ornithine decarboxylase activity increased markedly in both uninfected and vaccinia virus-infected HeLa cells following their transference to maintenance medium. The maximum level of activity in virus-infected cells was determined by the multiplicity of infection. These increases were completely inhibited by cycloheximide and partially inhibited by actinomycin D. In virus-infected cells only, treatment with FUdR resulted in prolonged expression of enzyme activity. The Km values for ornithine decarboxylase in uninfected and vaccinia virus-infected HeLa cells were significantly different. The mechanisms that may effect these changes are discussed.