title: The biotin requirement of HeLa cells.
abstract: We have examined the effect of alterations in the biotin content of the medium on the growth, viability, biotin content, and the activities of biotin-independent and biotin-independent enzymes of the HeLa cells. The inclusion in the growth medium of avidin, which almost irreversibly binds with biotin (Kd, 10(-15) M), results in an increase in cellular biotin content and biotin enzyme activity over that seen when the cells are grown in a biotin-depleted medium. The addition of avidin-bound biotin to the growth medium led to a forty-fold increase in cellular biotin when compared to the inclusion of an equivalent amount of free biotin in the medium. HeLa cells are able to internalize avidin-bound biotin. Biotin is released from this complex to function as the prosthetic group of biotin enzymes. HeLa cells do have a nutritional requirement for biotin.
mesh_terms: D001360:Avidin / Q000494:pharmacology; D001710:Biotin / Q000032:analysis / Q000494:pharmacology / Q000502:physiology*; D003470:Culture Media; D006367:HeLa Cells / Q000032:analysis / Q000201:enzymology / Q000502:physiology*; D006801:Humans
chemical_list: D003470:Culture Media; D001360:Avidin; D001710:Biotin