Substrate for the determination of E.coli dihydroorotase (EC 3.5.2.3.), which catalyzes the cyclization of carbamoyl-Asp-OH into L-5,6-dihydroorotate. This enzyme being in the biosynthetic pathway of pyrimidine nucleotides, is an important therapeutic target for the design of new antineoplastic agents. Its activity was assayed spectrophotometrically measuring the increase of absorbance at 230 nm (ε₂₃₀ = 1170 M⁻¹cm⁻¹, Km = 0.47 mM, kcat = 143 s⁻¹).