Metabolism of selenomethionine in selenium accumulator and non-accumulator astragalus species

The metabolism of selenomethionine in Astragalus crotalariae (a selenium-accumulating species) differs from that in Astragalus lentiginosus (a non-accumulator). After the administration of [⁷⁵Se]selenomethionine and [Me-¹⁴C]selenomethionine to excised leaves of A. crotalariae, Se-methylselenomethionine, Se-methylselenocysteine, and selenohomocystine were identified as the soluble components. A. lentiginosus formed mainly Se-methylselenomethionine, and a seleno peptide all of whose constituent amino acids have not been identified.When [³⁵S]methionine was administered to A. crotalariae a small amount was converted to S-methylmethionine but most was recovered as methionine. Homocrystine and S-methylcysteine were not formed in detectable amounts.