Isoleucine Serves as a Precursor for the Synthesis of β‐Alanine in Plants

Abstract

The non‐protein amino acid β‐alanine serves as an athletic performance enhancer and as a key precursor in the production of food additives and pharmaceuticals. In plants, β‐alanine is important for the synthesis of pantothenate (vitamin B5) and subsequently coenzyme A through a condensation reaction with pantoate. It is well established that the source of pantoate is valine, however the synthesis of β‐alanine in plants is less‐well established. There is some evidence that plants synthesize β‐alanine from spermine (or other poly‐amines), uracil, and propionate, but evidence has only been recorded in very specific plant systems, such as stress‐tolerant Limonium latifolium. In this project we sought to confirm the synthesis pathway of β‐alanine in Arabidopsis and the more economically relevant grain, wheat. We hypothesized that another branched‐chain amino acid, isoleucine, could serve as a source of β‐alanine in plants. Isoleucine degradation concludes with the production of propionyl‐CoA, which is further metabolized to acetyl‐CoA in a similar manner to β‐oxidation. Therefore, in order for isoleucine to serve as a precursor, the intermediate malonate semialdehyde must react via an unknown aminotransferase to produce β‐alanine. Using transgenic Arabidopsis plants and Hard Red Winter wheat, seedlings were treated with isotopically‐labeled precursors and extracts were analyzed by both NMR and GC‐MS. Results show that β‐alanine can be synthesized from both propionate and isoleucine via the proposed propionyl‐CoA metabolic pathway. Given these new findings and the prior evidence that valine serves as the precursor for pantoate, branched‐chain amino acids look to play an important role in the synthesis of pantothenate and coenzyme A in plants.Support or Funding InformationClare Boothe Luce Undergraduate Scholars program funded by the Henry Luce Foundation (Grant #9601), Kenyon Summer Science Scholars Program funded by Kenyon College, Kenyon Summer Science Cascade Program funded by the Sherman Fairchild FoundationThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.