METHIONINE-CONTAINING PEPTIDES CAN BE USED AS METHIONINE SOURCES FOR PROTEIN ACCRETION IN CULTURED C2C12 AND MAC-T CELLS

Twenty-two methionine-containing di- to octapeptides were evaluated fo r their ability to be a source of methionine to support protein accret ion in C2C12 myogenic and MAC -T bovine mammary epithelial cells. The cell cultures were incubated for 72 h at 37 degrees C in a humidified environment of 90% air:10% CO2 for C2C12 cells or 95% air: 5% CO2 for MAC-T cells. The basal medium contained methionine-free Dulbecco's mod ified Eagle's medium and 6% desalted fetal bovine serum. Treatments in cluded basal medium, the basal medium supplemented with one of the 22 methionine-containing peptides, or the basal medium supplemented with free L-methionine. Methionine-containing peptides with the exception o f glycylmethionine and prolylmethionine in C2C12 cells were able to su pport protein accretion with responses ranging from 29.1 to 123.3% of the response of L-methionine. Dipeptides with methionine at the N-term inus promoted greater (P < 0.0001) protein accretion than dipeptides w ith methionine at the C-terminus. Stimulation of protein accretion by seven pairs of dipeptides with methionine at either the C- or the N-te rminus was linearly (P < 0.0001) related to the hydrophobicity of the dipeptides. These results indicate that C2C12 myogenic and MAC-T mamma ry epithelial cells have the ability to utilize methionine-containing peptides as sources of methionine to support protein accretion.