News Brief
Studying Enzymes Crucial to Immunomodulation
June 17, 2025

Three important enzymes—indoleamine 2,3-dioxygenases (IDO1 and IDO2) and tryptophan dioxygenase (TDO)—are responsible for breaking down L-tryptophan, the least abundant essential amino acid in our bodies. In tumors, the overexpression of these enzymes helps the tumors evade the immune system by lowering tryptophan levels and producing molecules that weaken immune defenses, making the enzymes key targets for new cancer immunotherapies. Since enzymes play complex roles in both the immune system and metabolism, targeting them has posed a challenge.
Research led by Syun-Ru Yeh, Ph.D., and her team has improved our understanding of how these enzymes work at the molecular level. Dr. Yeh recently received a five-year, $3.3 million grant from the National Institute of General Medical Sciences to explore how the structures of these enzymes relate to their functions, how they are regulated by cellular metabolites, and how they affect health and disease. This work could lead to drugs for treating cancer as well as other diseases linked to dysregulated tryptophan metabolism.
Dr. Yeh is professor of biochemistry at Einstein. (1R35GM156326-01)