Amino acid metabolism in plants has been deemed a controversial topic, due to the lack of concrete evidence for any particular pathway. However, it has been suggested that enzymes related to the production and use of propionyl-CoA are involved. Associated with this is the metabolism of isobutyryl-CoA. These two molecules are deemed to be intermediates in valine metabolism. As propionate consists in the form of propionyl-CoA, it was discovered that propionyl-CoA is converted to β-hydroxypropionate through a peroxisomal enzymatic β-oxidation pathway. Nevertheless, in the plant Arabidopsis, key enzymes in the conversion of valine to propionyl-CoA were not observed. Through different experiments performed by Lucas et al., it has been suggested that in plants, through peroxisomal enzymes, propionyl-CoA (and isobutyryl-CoA) are involved in the metabolism of many different substrates (currently being evaluated for identity), and not just valine.