Baumrucker C R, Pocius P A
J Dairy Sci. 1978 Mar;61(3):309-14. doi: 10.3168/jds.S0022-0302(78)83599-1.
Lactating cow and rat tissues were examined for gamma-glutamyl transpeptidase. The specificity of the enzyme for various amino acid acceptors was determined for mammary tissue. The relative specific activity of gamma-glutamyl transpeptidase was high in cow mammary tissue and lower in rat mammary tissue in relation to the activity in kidney of the respective mammals. However, activity per gram wet weight of mammary tissues appeared equivalent. gamma-Glutamyl transpeptidase activity towards specific amino acids agreed with the percent extractions of these amino acids by the mammary gland of the lactating cow in vivo. We believe this is the first evidence of a possible system of amino acid transport by mammary tissues.
对泌乳母牛和大鼠的组织进行了γ-谷氨酰转肽酶检测。测定了该酶对乳腺组织中各种氨基酸受体的特异性。相对于各自哺乳动物肾脏中的活性，γ-谷氨酰转肽酶在母牛乳腺组织中的相对比活性较高，而在大鼠乳腺组织中较低。然而，每克乳腺组织湿重的活性似乎相当。γ-谷氨酰转肽酶对特定氨基酸的活性与泌乳母牛乳腺在体内对这些氨基酸的提取百分比一致。我们认为这是乳腺组织可能存在氨基酸转运系统的首个证据。
