Cyclic Changes in Enzyme Activity in Synchronized Mammalian Cell Cultures

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Science  09 Feb 1968:
Vol. 159, Issue 3815, pp. 634-636
DOI: 10.1126/science.159.3815.634


Activity of the enzymes glucose-6-phosphate dehydrogenase and lactate dehydrogenase increases intermittently in synchronized cultures of Chinese hamster cells. During G1 phase (3 hours after mitosis), midway through S phase (7 hours after mitosis) and again in late S phase (10 hours after mitosis), rapid increases in activity were observed and correlated with a net increase in cell size and total protein. The evidence suggests that this is a general phenomenon which affects a whole population of proteins and may be the expression of an endogenous cellular rhythm.