Isolation and kinetic properties of arginase in the gut of grasshopper (<i>Zonocerus variegatus</i> Linn)

Abstract

Arginase (EC 3.5.3.1) catalyzes the hydrolysis of arginine to ornithine and urea. Arginase was purified and characterized from the gut of Zonocerus variegatus through DEAE-cellulose and biogel-P100 gel filtration chromatography. The specific activity of the enzyme was 3.7 µmoles/min per mg of protein and a yield of 14.7%. An apparent molecular weight of 143,000 daltons was estimated by gel filtration on biogel P-100. The Michaelis constant (K m) of the enzyme was 40 mM with arginine as substrate. The optimum pH was 8.0 and the optimum temperature was 40 o C for Z. variegatus arginase. The enzyme was stable up to 40 o C for 20 min and lost all of its activity at 80 o C. The enzyme was specific for arginine as substrate. The enzyme was strongly enhanced in the presence of Mn 2+ , Na + , NH 4 + and Hg 2+ showed similar activation. Ni 2+ and Zn 2+ slightly inhibited Z. variegatus. Chelating (EDTA, citrate, ascorbic acid and urea) and thio (2-mercaptoethanol and cystein) compounds inhibited the activity of arginase in Z. variegatus. While amino acids (proline, lysine, aspartate and valine) showed no inhibition on arginase activity. The presence of arginase in the gut of Zonocerus variegatus could be for other functions rather than urea production in urea cycle.

Insectes ravageurs et champignons parasites associés au dépérissement des peuplements de <i>Tectona grandis</i> (teck) régénérés à Téné, zone semi-décidue de Côte d’Ivoire

“…Par ailleurs, au cours de nos inventaires de terrain, nous avons observé la présence de Zonocerus variegatus dans la végétation environnante (Talinum triangulare, Aspilla lacifolis, Aspilla africana, Tridax esculenta, Chromolaena odorata) mais également dans les champs de Manihot esculenta. Les feuilles de ces espèces contribuent a la croissance de Zonocerus variegatus(Okonji et al, 2013) Cela démontre le caractère polyphage du criquet puant. Des études réalisées parJames et al (2015) ont montré que Zonocerus variegatus était attiré par différentes plantes contenants des alcaloïdes de pyrrolicidines dont le criquet s'en sert pour se protéger chimiquement ainsi que ses oeufs contre les parasites.…”

Study Some Kinetic Parameters for Purified Arginase from Two Different Sources: Red Blood Cells and Serum of( Healthy and TypeII Diabetic Patient)

“…It can be noticed that enhancing substrate concentration enhances the rate of the reaction because of increasing the collisions between substrate and enzyme molecules until reaching a certain concentration, after that further increasing in substrate concentration has no effect on the reaction rate because that enzyme becomes saturated and its active site is occupied with substrate concentration become without effect on the reaction rate, because the enzyme becomes saturated, and the active site is occupied with the substrate [9] . Ferit [10] states that Km value for arginase purified from human vitreous humor is 6 mM to L-arginine, Okonji et al [11] and Okonji, et al, [12] report that K m value to L-arginine monochloride is 250mM, with Vmax of 6.7 µg /min for arginase purified from the gut of grasshopper, and found that the K m value is 66.7 mM for arginase purified from liver of tortoise. Ezima et al, [13] found that the K m to be 17mM for arginine and Vmax value to be 1.39 µmole ml -1 min -1 for arginase purified from fruit bat liver.…”