Thesis Abstract

Cyanide is known to be one of the most toxic substances present in a wide variety of food materials that are consumed by animals.One of the cyanide detoxifying enzymes is 3-mercaptopyruvate sulfurtransferase (3-MST). Indeed, recent studies have clearly shown that 3-MST is involved in the detoxification of cyanide.Rhinoceros (Oryctes rhinoceros) larva feeds on dead, decayed and living plants, wood and palm. Plants are known to contain cyanide as a defence mechanism for intruding/pesting organisms. Thus, for rhinoceros larva to be able to live on plants, it must have possessed a cyanide-detoxifying enzyme.3-MST, a cyanide-detoxifying enzyme was purified from Rhinoceros (Oryctes rhinoceros) larva in this work.The 3-MST enzyme was isolated from the gut of Oryctes rhinoceros larvae and purified using Ammonium Sulphate Precipitation, Bio-Gel-P-100 Gel Filtration Chromatography and Reactive Blue-2-Agarose Affinity chromatography.The specific activity of the enzyme was 0.22U/mg.The presence of this enzyme could be exploited by including it in the diet of animals which would serve as a source of protein and 3-MST. Perhaps, these rhinoceros larva could be introduced on farmland with contaminated soil whereby they will process the dead roots and plants into soil thereby providing more space and manure for plants to grow healthy.

Thesis Overview

INTRODUCTION One of the major metabolic enzymes that have gained so much interest of scientists is 3-Mercaptopyruvate sulfurtransferase (3-MST). This enzyme occurs widely in nature (Bordo, 2002 and Jarabak, 1981).It has been reported in several organisms ranging from humans to rats,fishes and insects. It is a mitochondrial enzyme which has been concerned in the detoxification of cyanide, a potent toxin of the mitochondrial respiratory chain (Nelson et al., 2000). Among the several metabolic enzymes that carry out xenobiotic detoxification, 3-mercaptopyruvate sulfurtransferase is of utmost importance.3-mercaptopyruvate sulfurtransferase functions in the detoxifications of cyanide; mediation of sulfur ion transfer to cyanide or to other thiol compounds.(Vanden et al., 1967). It is also required for the biosynthesis of thiosulfate. In combination with cysteine aminotransferase, it contributes to the catabolism of cysteine and it is important in generating hydrogen sulphide in the brain, retina and vascular endothelial cells (Shibuya et al., 2009). It also acquired different functions such as a redox regulation (maintenance of cellular redox homeostasis) and defense against oxidative stress, in the atmosphere under oxidizing conditions Nagahara et al (2005).Hydrogen sulphide (H2S) is an important synaptic modulator, signalling molecule, smooth muscle contractor and neuroprotectant (Hosoki et al., 1997).Its production by the 3-mercaptopyruvate sulfurtransferase and cysteine aminotransferase pathways is regulated by calcium ions (Hosoki et al., 1997). Organisms that are exposed to cyanide poisoning usually have this enzyme in them. This could be in food as in the cyanogenic glucosides being consumed. It has been studied from variety of sources, which include bacteria,yeasts, plants, and animals (Marcus Wischik, 1998). Cyanide could be released into the bark of trees as a defence mechanism.There are array of defensive compounds that make their parts (leaves, flowers, stems, roots and fruits) distasteful or poisonous to predators. In response,however, the animals that feed on them have evolved over successive generations a range of measures to overcome these compounds and can eat the plant safely. The tree trunk offers a clear example of the variety of defences available to plants (Marcus Wischik, 1998).Oryctes rhinoceros larva is one of the organisms that are also exposed to cyanide toxicity because of the environment they are found.