The activity of L-ornithine decarboxylase (L-ornithine carboxy-lyase; EC 18.104.22.168), the enzyme that catalyzes the initial and rate-limiting step in polyamine biosynthesis, has been studied in Chinese hamster ovary fibroblasts synchronized by selective detachment of mitotic cells. At various times after plating the distribution of cells among the G1, S and G2+M phases of the cell cycle was calculated from DNA distributions obtained by high-speed flow cytometric analysis. At these same times determination of the cellular L-ornithine decarboxylase activity showed that polyamine (putrescine) synthesis was initiated in mid-G1, that the rate of synthesis was maximal prior to DNA synthesis, and that it decreased during the S phase. A second increase in enzyme activity occurred before mitosis.
|Original language||English (US)|
|Number of pages||7|
|Journal||Biochemical and Biophysical Research Communications|
|State||Published - Jul 12 1976|
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology