Biochemical studies on the synthesis of histidine in the liver and kidney of cattle

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Establishment of essential amino acids in higher animals rendered considerable contributions to enhancement of productivity in livestock and maintenance of normal growth and health in human beings. In ruminants like cattle, however, essential amino acids have never been completely established due to the technical uneasiness in experiments. In this study, it was examined whether or not histidinol dehydrogenase (HLDase) activities can be found in the livcr and some other organs of cattle in order to prove an ability to synthesize histidine of ruminant animals. Cattle organs were obtained from slaughter house. HLDase was assayed by an increase in histidine from histidinol added as a substrate after incubation at 37℃ for a constant period. Histidine was quantitatively determined by an HPLC method. In 2001, the activity of the liver was assayed at first and shown to have optimal pH at 9.5. Using the value, an ability to synthesize histidine of the liver was estimated to be about 14 g/day provided that the cattle with about 700 kg of body weight have about 7 kg of liver. In 2002, the activities of the kidney, pancreas, spleen, muscle and mucous membrane of small intestine were assayed. The activity per unit weight of each organ was highest in the liver followed by kidney, pancreas, spleen, muscle and small intestine in this order. The production of histidine in the liver, kidney and muscle was calculated to be 30.8 g/day assuming that the weights of kidney and muscle of the cattle might be about 1.3 and 300 kg, respectively. Then the requirement of histidine of the cattle is provisionally estimated to be 14.6 g/day from the requirement of DCP and the histidine content in beef muscle protein. Thus the cattle seemed to serve histidine by themselves. HLDase activities were also observed in the liver, kidney and muscle of swine, mouse, fowl and wild duck, but the production of histidine seemed less than their requirements of histidine.