Beta-alanine synthesis occurs in the cytosol either from the catabolism of the pyrimidine uracil or from the decarboxylation of L-aspartate. In the ommatidia, beta-alanine is required for histamine recycling: ebony (e) catalyses the condensation of histamine with beta-alanine to form carcinine, which is then hydrolysed by tan (t) to regenerate free histamine. In epidermal cells, beta-alanine is conjugated with dopamine to form N-beta-alanyl dopamine (NBAD), a metabolite involved in the pigmentation and sclerotization of the cuticle. (Adapted from FBrf0217847.)