Abstract
The present experiments were conducted to examine if histidinol dehydrogenase (HLDase) activity could be detected in the liver and kidney of cattle, in order to assess the possibility that cattle synthesize histidinc (His) de novo. Crude enzyme solutions of liver and kidney from Japanese black cattle showed HLDase activities with pH optima of 11.0 and 9.0, respectively. This is the first report of HLDase activity in animal tissues. The amount of His produced from histidinol (HDL) by the enzymes of the liver and kidney were calculated to be sufficient for meeting the His requirement of the cattle, based on the crude protein requirement for the animals and His content in muscle protein. In contrast, HLDase activities in swine liver and kidney proved to be insufficient to form sufficient His from HDL to meet their requirement as indicated in the Japanese Feeding Standard for Swine (1998).
