Glutathione Accumulation in Lactococci

Glutathione accumulation was quantified in cell-free extracts prepared from Lactococcus lactis ssp. cremoris C2 and Z8 cultures grown in milk and milk supplemented with the AA precursors to glutathione or to glutathione. Accumulation of glutathione was detected with Z8 in all three media (5.6, 12, and 470 nmol! mg of protein, respectively); however, no accumulation of glutathione was detected with C2. After growth of these strains in defined broth and defined broth supplemented with glutathione or the glutathione precursors, only the cellfree extract of Z8 grown with glutathione supplement contained detectable amounts of glutathione (372 nmol/mg protein). When [35S]Cys was added to the defined broth containing the glutathione AA precursors, neither strain accumulated [35S]glutathione. Supplementation of the defined broth with [35S]glutathione resulted in accumulation of [35S]glutathione in Z8, but not in C2. Although Z8 can transport glutathione, it is not capable of glutathione synthesis. However, C2 is incapable of both glutathione transport and glutathione synthesis. Additionally, Z8, C2, and a variety of other lactic acid bacteria were examined for -y-glutamyl-transferase activity; no activity was observed with any of the lactic acid bacteria examined.