Comparative physical-chemical studies of mammalian arginases

1. 1. Liver arginase (E.C. 3.5.3.1) of various mammalian species (rat, mouse, dog, rabbit, pork, monkey) were partly purified and their isoelectric properties determined by carboxymethyl cellulose column chromatorgraphy and isoelectric focusing. 2. 2. The ureotelic arginase can be divided into mainly two groups; (i) basic and (ii) slightly acidic or neutral proteins. 3. 3. The two groups of arginases showed marked differences in the binding of Mn 2+. 4. 4. Only beef liver arginase could be activated by Co 2+ and Ni 2+, all other mammalian arginases were inhibited by these metal ions. 5. 5. The molecular weights were found to range from 120,000–160,000 daltons. 6. 6. High Michaelis constanta (6–20 mM) were obtained for all arginases studied. 7. 7. Similarities were also found in the pH optima (pH 9·3–10·5) as well as the optimal Mn 2+ concentration (40 mM) required to obtain maximal catalytic activity.