furthermore , we demonstrated the presence in quiescent cells of an na+-dependent transport system for neutral amino acids that has been characterized as system asc by several criteria including intolerance to methylaminoisobutyric acid , strict na+-dependence , the property of transtimulation and specificity for pertinent substrates such as alanine , serine , cysteine and threonine .
C0301715
neutral amino acids
C0036720
serine