Arginase acts as a mediator in the final phase of the urea cycle, protecting against excessive ammonia under homeostatic conditions by producing L-ornithine and urea. In this study, the physicochemical properties of Oryctes rhinoceros Larva arginase were investigated for biochemical comparison with its well-studied terrestrial mammalian. Oryctes rhinoceros larva arginase was isolated and purified to homogeneity. The purification procedure involved ion-exchange chromatography on DEAE-cellulose and affinity chromatography on reactive Blue 2-agarose. The pure enzyme had a specific activity of 38.7 U/mg, a purification fold of 63.4, and a percentage yield of 16.5%. O. rhinoceros gut arginase had a native and subunit molecular weight of 82 and 45 kDa, respectively and the Km and Vmax were 11.25 mM and 13.055 μmmol/min/mL, respectively. The activity was optimum at 60 °C m max (pH 8). The enzyme retained more than 60% of its activity at 50 °C for 60 min. The inhibition study on the enzyme showed that cations salts (CaCl2 , BaCl2 , HgCl2 , and SnCl2 ) enhanced the enzyme activity at 1 mM concentration except for SnCl2 . EDTA, a chelating compound, strongly inhibited the activity of the enzyme. The 2 effect of different amino acids on activity showed that L-valine, L-serine, L- aspartic acid, and L-glutamic acid had a moderate inhibitory (60%, 63%, 65.4%, 69.1%, respectively) effect on the enzyme activity. The study concluded that there were similarities between O. rhinoceros larva arginase and those of other ureotelic animals in terms of kinetics and physicochemical properties.

Cyanide pollution of aquatic environment has become a great concern in Nigeria because of the increase in cassava cultivation. In Nigeria, cassava processing milling plants are usually situated around streams or rivers such that the waste from each stages of processing easily find their way into these water bodies as effluents and waste waters. Extracellular rhodanese of Klebsiella edwardsii isolated from Atutulala stream, Modakeke, where cassava is being processed, was assessed for its bioremediation potential. Cyanide concentration of the stream was analysed for six months. Four bacterial isolates were screened for their ability to degrade free cyanide and the best strain was further screened for rhodanese producing ability. The enzyme was purified by 85% ammonium sulphate precipitation and diethyl aminoethyl-cellulose ion-exchange chromatography. The pure enzyme had a specific activity of 0.0473 Rhodanese Unit mg-1 with a purification fold of 4.56 and a percentage yield of 30.30%. The enzyme demonstrated a broad pH range but the optimum pH was at 6.0 while the optimum temperature was 60°C. The bioremediation potential of the enzyme was assessed under various conditions such as the field pH and temperature as well as optimum pH and temperature using the cyanide contaminated water as substrate source in a typical assay protocol. The enzyme was able to convert 1.6481 µmol of cyanide to thiocyanate in the water sample at optimum pH and temperature of the enzyme. It could be concluded from the study that at optimum pH and temperature, rhodanese exhibited remediation activity in cyanide contaminated aquatic ecosystems and thus, can be used for its restoration.