Isolation and properties of arginase from a shade plant, ginseng (Panax ginseng CA Meyer) roots

Arginase (EC 3.5.3.1) was purified to homogeneity from root tissues of three-year-old ginseng (Panax ginseng C.A. Meyer), shade plant, and was found to be an extraordinarily large molecule relatively stable to heat. The enzyme was decameric having a molecular mass of 352,000 Da, with an optimal temperature and pH of 60 degreesC and 9.5, respectively. Analogues of arginine could not replace it as substrate, and a cysteine residue is at or near the active site. Maximum activity was obtained with Mn2+ and Co2+ also activated the proteins, whereas, both agmatine and 5'-deoxy-methylthioadenosine were inhibitors. Specific activities of the enzyme in sliced ginseng roots were increased by plant hormones such as GA(3), IAA, kinetin and putrescine, whereas the activities of the purified enzyme were unaffected by putrescine. Increases in arginase activities by these plant hormones could affect metabolism of polyamine intracellularly. (C) 2001 Elsevier Science Ltd. All rights reserved.