Effects of methionine and its ratio to lysine on expression of αs1 casein gene in cultured bovine mammary epithelial cells

Abstract

Effects of methionine dose and its ratio to lysine on αs1 casein gene expression were evaluated in cultured bovine mammary epithelial cells. Methionine was added at levels of 0-100 μg/ml and ratio of lysine to methionine was set at 1-4.5:1. Expression of αs1 casein gene was enhanced by addition of methionine up to 60 μg/ml, and then leveled off. There was an increasing trend in αs1 casein expression with the increasing ratio of lysine to methionine and the highest level was at 3.5:1. These results indicated that adequate quantities and ratio of amino acids are required to promote milk protein synthesis.