Differential expression of multiple forms of arginase in cultured cells

Arginase (EC 3.5.3.1), the final enzyme in the urea cycle, catalyzes the cleavage of arginine to orthinine and urea. At least two forms of this enzyme, AI and AII, have been described and are probably encoded by discrete genetic loci. The expression of these separate genes has been studied in mammalian cells grown in culture. The permanent rat-hepatoma line H4-II-E-C3 contained exclusively the AI enzyme; the form in mammals comprising about 98% of the arginase activity in liver and erythrocytes but catalyzing only about one half of that reaction in kidney, gastrointestinal tract, and brain. By contrast, human-embryonic-kidney and -brain cells, after transformation with the human papovavirus BK, contained only the AII species of arginase, which form contributes the remaining half of that catalysis in those mammalian tissues in vivo. We report here the results of an extensive study on the properties of these two forms of arginase in the three cell lines, including Km values for arginine, behavior on polyacrylamide gels under non-denaturing conditions, and cross-reactivity with lapine antibodies against the arginases from either rat or human liver.