title: Cysteine auxotrophy of human leukemic lymphoblasts is associated with decreased amounts of intracellular cystathionase protein.
abstract: A series of human lymphoblastoid cell lines derived from nonleukemic donors are known to be cysteine prototrophs (cys+), while several lymphoblastoid lines derived from leukemic donors are cysteine auxotrophs (cys-). We have tested representative cell lines of each type for their content of cystathionase enzyme activity by a specific catalytic assay and their total cystathionase protein content by immunoprecipitation of in vivo labeled protein. There was a close correlation between the cellular content of the enzyme as determined in the two assays. Specifically, those cys+ lines having readily measureable enzyme by catalytic assay were found to contain significantly higher levels of immunoprecipitable Mr 43 000 cystathionase subunit than those cys- lines tested which were depleted in active enzyme. Thus, the absolute cysteine requirement of the leukemic, cys- cell lines tested is likely due to an intracellular reduction of cystathionase protein.
mesh_terms: D000936:Antigen-Antibody Complex; D002460:Cell Line; D003542:Cystathionine gamma-Lyase / Q000097:blood*; D003545:Cysteine / Q000097:blood*; D006801:Humans; D007106:Immune Sera; D007118:Immunoassay; D007938:Leukemia / Q000378:metabolism*; D008099:Liver / Q000201:enzymology; D008190:Lyases / Q000097:blood*; D008214:Lymphocytes / Q000378:metabolism*; D008970:Molecular Weight
chemical_list: D000936:Antigen-Antibody Complex; D007106:Immune Sera; D008190:Lyases; D003542:Cystathionine gamma-Lyase; D003545:Cysteine