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Effect of Hydroquinone on Ruminal Urease in the Sheep and its Inhibition Kinetics in vitro |
Y. G. Zhang, A. S. Shan, J. Bao |
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Abstract |
Effect of hydroquinone (HQ) on rumen urease activity was studied. Hydroquinone at concentrations of 0.01 ppm, 0.1 ppm, 1 ppm, and 10 ppm inhibited urease activity of intact rumen microbes in vitro by 25%, 34%, 55% and 64% respectively. In the presence of low concentrations of -mercaptoethanol, rumen urease could be solubilized and partially purified. The Km for the enzyme was 2 10-3 M with Vmax of 319.4 moles/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 concentrations indicating a noncompetitive effect in nature with an inhibition constant 1.2 10-5 M. Hydroquinone at the concentration of 10 ppm produced 64% urease inhibition, did not affect ruminal total dehydrogenase and proteolytic enzyme (p>0.05), but increased cellulase activity by 28% (p<0.05) in vitro. These results indicated that hydroquinone was a effective inhibitor of rumen urease and could effectively delay urea hydrolysis without a negative effect. The inhibitor appeared to offer a potential to improve nitrogen utilization by ruminants fed diets containing urea. |
Keywords:
Hydroquinone; Ruminal Urease; Inhibition Kinetics; Sheep |
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