Evaluation of optimal conditions for arginase activity in streptozotocin induced diabetic rats

Abstract

The assay conditions needed to achieve maximal activity of liver and kidney arginase in diabetic and non-diabetic rats were investigated and compared. The physicochemical and kinetic properties of liver arginase in diabetic and control rats were very similar, those of kidney arginase were significantly different. It was found that preincubation temperature (68°C), preincubation period (20 min), optimum pH (10.1) of liver arginase and K<sub>m</sub> (3.2) for its substrate, L-arginine, did not change in diabetic and non-diabetic rats. As a consequence of diabetes, the optimum Mn<sup>2+</sup> concentration for liver arginase only changed from 1 to 2 mM. Although the preincubation temperature and period for activation of kidney arginase in control rats was unnecessary, they were found to be 56ºC and 12 min in diabetic rats. The pH profile of arginase in kidney of diabetic rats was different from that of control rats. The K<sub>m</sub> value (6.7) of arginase for L-arginine in kidney is unchanged in diabetes whereas a marked decrease in V<sub>max</sub> was found. Optimum Mn<sup>2+</sup> concentration (2 mM) for kidney arginase was unchanged in diabetes. The activity of arginase in liver of diabetic animals was higher 1.5 to 1.7 times than that of controls. Diabetes caused an about 53% decrease of arginase activity in kidney of female rats, 26% in that of males. These findings may suggest an idea that encoded arginases by separate gene loci may be affected differently by the pathological and hormonal status.

Purification and Characterization of Arginase from Serum of Healthy and Type II Diabetic Iraqi Patients

“…[17] report that the optimum pH of human serum 9.2-9.6. Generally arginases of mammalian are previously show to have basic optimum pH (9.5-10.5) [18] and that is predominantly attributed to that the enzyme active sit composed from basic amino acids [19] . The variance in activity with pH proposes that at the catalytic site an ionisable group may function [7] .…”

Disturbance of Arginase Activity and Nitric Oxide Levels in Iraqi Type 2 Diabetes Mellitus

“…our results are also compatible with the result of Shatanawi et al(2) who found that arginase activity was elevated in 62 patients with T2DM as compared to age-matched healthy volunteers. Diabetes is accompanied by increased food consumption, amino acid metabolism and ratio of blood glucagon to insulin, all of which would tend to increase the activity of the urea cycle as well as arginase activity (21).…”