title: Isolation of mutants lacking branched-chain amino acid transaminase.
abstract: Variants of the Chinese hamster ovary cell have been isolated which can no longer grow when valine, leucine, or isoleucine is replaced in the culture medium by its respective alpha-keto acid: alpha-ketoisovaleric acid, alpha-ketoisocaproic acid, or alpha-keto-beta-methylvaleric acid. These variants lack branched-chain amino acid transaminase activity. Evidence is presented indicating these variants to be single gene mutants. Genetic evidence is also presented confirming previous biochemical evidence that a single enzyme carries out transaminase functions on valine, leucine, and isoleucine. The branched-chain transaminase-deficient (trans-) mutants can be reverted to wild-type behavior by treatment with mutagenic agents. These mutants promise to be useful in exploring regulatory mechanisms in biochemical, genetic, and cancer research.
mesh_terms: D002460:Cell Line; D004790:Enzyme Induction; D007532:Isoleucine / Q000378:metabolism; D007930:Leucine / Q000378:metabolism; D009154:Mutation / Q000528:radiation effects; D010641:Phenotype; D000637:Transaminases / Q000378:metabolism*; D014466:Ultraviolet Rays; D014633:Valine / Q000378:metabolism
chemical_list: D007532:Isoleucine; D000637:Transaminases; D007930:Leucine; D014633:Valine