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Effect of hydropuinone (HQ) on rumen urease acivity was studied. Hydroquinone at concentration of 0. 01 mg· L-1 , 1 mg· L-1and 10 mg · L-1 inhibited urease of intact rumen microbes in vitro by 25%, 34%,55% and 64% respectively. In the present of low concentration of βmercaptoethanol, rumen urease could be solubilized and partially purified. The Km for the enzyme was 2 × 10-3 mol · L-1 with Vmax of 319. 144μmoles/mg/min. The kinetics of inhibition with partially purified rumen urease was investigated. The result showed that the inhibitory effect was not eliminated by increasing urea concentration indicating a noncompetitive in nature with inhibition constant 1.2 × 10-5mol · L-1. Hydropuinone at a concentration that produced 64% urease inhibition did not affect ruminal total dehydrogenase, proteolytic enzyme( P ＞ 0. 05) but increased cellulase activity by 28% ( P ＜ 0. 05 ) in vitro. These results demonstrated that hydropuinone was a specific inhibitor of rumen urease and could delay urea hydrolysis effectively without negative effect. The inhibitor appeared to offer the potential to improve nitrogen utilization by ruminants fed diets containing urea.