mTOR is a target molecule in mammalian used in rapamycin drug and it has been recognized as a central molecule that has a role of signaling for regulating proliferation and cell growth. Since DNA replication is essential for proliferation, regulating system of cell growth and amino-acid perception centrally related with mTOR deeply involve with the system of biosynthesis of nucleic acid. CAD (carbamoyl phosphate synthetase, aspartate transcarbamoylase, dihydroorotase) was discovered and found its important roles in the pathway of pyrimidine biosynthesis as a result of survey for molecules related to biosynthesis of nucleic acid in a molecular complex with raptor and mLST8. CAD catalyzes an initial step in de novo synthesizing system of pyrimidine synthesis and it is regulated by phosphorylation of other protein kinases. mLST8 bridges between CAD and mTOR and CAD plays a role as signaling in mTOR pathway by a cross-interaction with mLST8. This antibody is considered as a useful tool for research in mTOR signal pathway, especially for research in regulating system of biosynthesis of nucleic acid.