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

高等动物必需氨基酸的建立对提高牲畜生产力和维持人类的正常生长和健康作出了重大贡献。然而，在像牛这样的反刍动物中，由于实验中的技术问题，必需氨基酸从未完全确定。为了证明反刍动物具有合成组氨酸的能力，本研究检测了牛肝脏和其他器官中是否存在组氨酸脱氢酶（HLDase）活性。牛的器官是从屠宰场获得的。在37℃恒温培养一段时间后，通过添加组氨酸作为底物来增加组氨酸来测定HLDase。采用高效液相色谱法定量测定组氨酸。2001年，首次测定了肝脏的活性，结果显示最佳pH值为9.5。利用这一数值，假设体重约700公斤的牛有约7公斤的肝脏，肝脏合成组氨酸的能力估计约为14克/天。2002年，对肾脏、胰腺、脾脏、肌肉和小肠粘膜的活动进行了测定。各器官单位重量活性最高的是肝脏，其次是肾脏、胰腺、脾脏、肌肉和小肠。以牛的肾脏和肌肉体重分别约为1.3 kg和300 kg计算，肝脏、肾脏和肌肉中的组氨酸产量为30.8 g/d。根据牛对DCP的需要量和牛肉肌肉蛋白中组氨酸的含量，初步估计牛对组氨酸的需要量为14.6 g/d。因此，牛群似乎自己就能提供组氨酸。在猪、小鼠、家禽和野鸭的肝脏、肾脏和肌肉中也观察到HLDase的活性，但组氨酸的产量似乎低于它们对组氨酸的需求量。

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.