Methionine utilization in long‐term human lymphoid cell lines

Long‐term lymphoid cell lines (LTL) cultured under normal conditions use methionine primarily for protein synthesis, although a significant proportion is converted to S‐adenosylmethionine (SAM) and used for synthesis of the polyamines, spermidine, and spermine. When LTL are cultured under conditions of high cell density, there is an initial phase of rapid protein synthesis and accumulation of SAM as found under normal culture conditions, but this soon ceases. Polyamine synthesis is small under these conditions, despite the presence of relatively large amounts of SAM.