Assay of urea is provided by spectrophotometric measurement of a test solution containing the urea to be assayed together with ATP: urea amido-lyase and adenosine triphosphate as co-substrate for the enzyme, together with nicotine adenine dinucleotide, reduced; phosphoenol pyruvate; lactate dehydrogenase; pyruvate kinase; and magnesium and potassium ions. The transformation of the urea is followed quantitatively by optical absorption measurements at 340 millimicrons. The assay is unaffected by the presence of non-urea nitrogen, such as ammonia.
A composition, device and method useful as an enzymatic urea assay based on the use of urea amidolyase comprising urea amidolyase, pyruvate kinase, pyruvate oxidase, mono and divalent cations, phosphoenolpyruvate, thyamine pyrophosphate, ATP, bicarbonate, phosphate, a color indicator system and optionally inorganic phosphate, a buffer having a pH range of from about 6.5 to 9.5, and sodium or potassium ferrocyanide. After contacting the test solution or body fluid sample with the assay composition, reading can be accomplished visually or instrumentally.
