Arginase 1 (ARG1) is a 35-40kD member of the arginase family of enzymes.
It is expressed in multiple cell types, including erythrocytes, hepatocytes, neutrophils, smooth muscle and macrophages.
ARG1 demonstrates two distinct functions: in the hepatocyte cytoplasm, it catalyzes the conversion of arginine to ornithine and urea, while in multiple cells, it degrades arginine, thus indirectly down-regulating NO synthase (NOS) activity by depriving this enzyme of its substrate.
Human ARG1 is 322aa in length.
Its enzyme region comprises aa9-309 and contains two Mn atoms.
ARG1 is modestly active as a monomer, but highly active as a 105kD homotrimer.
Trimerization is promoted by nitrosylation of Cys303, creating a regulatory feedback loop with NOS.
There are two isoform variants, one that shows an eight aa insertion after Gln43, and another that shows a deletion of aa204-289.
Full-length human ARG1 shares 87% aa identity with mouse and rat ARG1.