Genetic studies in mouse and human suggest that kynureninase activity may influence blood pressure and renal function. The gene coding kynureninase (KYNU) is also located on chromosome band 2q14-q23, where a linkage peak for essential hypertension was previously detected in the Chinese Han population.The results show that the rare KYNU variant Arg188Gln affects kynureninase activity and are consistent with the hypothesis that this mutation can predispose to essential hypertension.