Enzymes of Krebs-Henseleit Cycle in Vitis vinifera L: III. In Vivo and In Vitro Studies of Arginase.

The presence of arginase (EC 3.5.3.7) in various tissues from Vitis vinifera L. cultivars was demonstrated by both in vivo and in vitro enzyme assays. Initial velocities determined by the two methods were in close agreement. Optimum conditions for maximum enzyme activity were 25 to 30 millimolar l-arginine, about 1 millimolar Mn(2+) (pH 9.4 to 9.8), and incubation temperature of 37 to 38 C. l-Arginine hydrolysis was linear with increasing sliced fresh tissue up to 500 milligrams for in vivo assay, and with enzyme extract equivalent up to about 200 milligrams of fresh tissue for in vitro. Similarly, l-arginine hydrolysis was linear with incubation time for the first 45 minutes for in vivo assay and for the first 20 minutes for in vitro.