Clark R M, Chandler P T, Park C S
J Dairy Sci. 1978 Apr;61(4):408-13. doi: 10.3168/jds.S0022-0302(78)83614-5.
Experiments are presented to determine the effect of labeled precursor amino acid on synthesis of beta-lactoglobulin and beta-casein and to identify the most limiting amino acids in Eagle's minimal essential medium for synthesis of milk protein. Protein synthesis was measured by incorporation of carbon-14 labeled amino acids into milk protein from bovine mammary cell culture. Mammary tissue from 13 Holsteins (12.7 kg milk/day) was dispersed and cultured for 18 h. In Experiment 1, three replications (cows) with three amino acid mixtures, utilizing labeled lysine or leucine as the marker amino acid, showed that labeled lysine overestimated the effect of medium lysine, and labeled leucine overstimated the effect of leucine on beta-lactoglobulin and beta-casein synthesis. Subsequently Experiment 2 utilized 10 replications (cows) to determine the effect of a three-fold increase of each of 13 amino acids in Eagle's medium. Increased threonine or methionine improved beta-lactoglobulin synthesis and cystine increased beta-casein. Second and third best response in beta-casein were from addition of methionine and threonine. Combined analysis from 10 cows and two protein responses by multivariate procedures identified, in order of decreasing magnitude, cystine, threonine, and methionine as limiting amino acids in the dispersed cell culture.
本文介绍了一些实验，以确定标记的前体氨基酸对β-乳球蛋白和β-酪蛋白合成的影响，并确定伊格尔氏基本培养基中合成乳蛋白时最具限制性的氨基酸。通过将碳-14标记的氨基酸掺入牛乳腺细胞培养物中的乳蛋白中来测量蛋白质合成。将13头荷斯坦奶牛（日产奶量12.7千克）的乳腺组织分散并培养18小时。在实验1中，使用标记的赖氨酸或亮氨酸作为标记氨基酸，对三种氨基酸混合物进行了三次重复实验（奶牛），结果表明，标记的赖氨酸高估了培养基中赖氨酸的作用，而标记的亮氨酸高估了亮氨酸对β-乳球蛋白和β-酪蛋白合成的影响。随后，实验2使用了10次重复实验（奶牛）来确定伊格尔氏培养基中13种氨基酸各自增加三倍的效果。苏氨酸或蛋氨酸的增加改善了β-乳球蛋白的合成，胱氨酸增加了β-酪蛋白的合成。β-酪蛋白的第二和第三最佳反应来自添加蛋氨酸和苏氨酸。通过多变量程序对10头奶牛和两种蛋白质反应进行的综合分析确定，在分散细胞培养中，按限制程度从大到小依次为胱氨酸、苏氨酸和蛋氨酸是限制性氨基酸。
