5′-Nucleotidase — An Overview of the Last Three Years

Abstract

There have been many exciting developments regarding the structure, function, and regulation of 5′-nucleotidase (5′-NT) during the three years since the 6th International Symposium on Purine and Pyrimidine Metabolism in Man. First, the gene for 5′-NT was cloned and sequenced from both rat liver and human placenta by Dr. Yukio Ikehara and colleagues^1,2. The sequencing of the gene, along with other structural information^3,4, has led to the confirmation that 5′-NT is indeed anchored into the plasma membrane via covalent linkage to glycosyl phosphatidylinositol (GPI). Second, 5′-NT was assigned to cluster of differentiation #73 (CD73) by the Fourth International Workshop on Human Leukocyte Differentiation Antigens⁵. The assignment of a CD number gives new stature to 5′-NT as a lymphocyte differentiation antigen in the eyes of the immunological community. Furthermore, the availability of uniform reagents will greatly facilitate studies of the expression and function of this interesting molecule on lymphocytes, as well as in other tissues. New insight into the function of 5′-NT comes from the observation that purified enzyme from chicken gizzard can serve as a receptor for the extracellular matrix proteins fibronectin and laminin^6,7 and from the finding that anti-5′-NT antibodies cause activation of human lymphocytes^8,9. I will use the terms 5′-NT and CD73 interchangably.