Queuine promotes antioxidant defence system by activating cellular antioxidant enzyme activities in cancer

Abstract

Constant generation of Reactive oxygen species (ROS) during normal cellular metabolism of an organism is generally balanced by similar rate of consumption by antioxidants. Imbalance between ROS production and antioxidant defense results in increased level of ROS causing oxidative stress which leads to promotion of malignancy. Queuine is a hyper modified base analogue of guanine, found at first anti-codon position of Q- family of tRNAs. These tRNAs are completely modified with respect to queuosine in terminally differentiated somatic cells, however hypomodification of Q-tRNAs is close association with cell proliferation. Q-tRNA modification is essential for normal development, differentiation and cellular functions. Queuine is a nutrient factor to eukaryotes. It is found to promote cellular antioxidant defense system and inhibit tumorigenesis. The activities of antioxidant enzymes like catalase, SOD, glutathione peroxidase and glutathione reductase are found to be low in Dalton's lymphoma ascites transplanted (DLAT) mouse liver compared to normal. However, exogenous administration of queuine to DLAT mouse improves the activities of antioxidant enzymes. The results suggest that queuine promotes antioxidant defense system by increasing antioxidant enzyme activities and in turn inhibits oxidative stress and tumorigenesis.

Dietary Intake ofCurcuma longaandEmblica officinalisIncreases Life Span inDrosophila melanogaster

“…However, overexpression of catalase in mitochondria, nucleus, or peroxisomes has been shown to increase lifespan of mice [38, 39]. CAT enzyme plays crucial roles as antioxidants and constitutes the primary defense system against the toxic effects of superoxide radicals (O2−) in organisms [40]. According to the most acceptable free radical theory of aging, the potentially toxic-free radicals, primarily the ROS, superoxide, and hydroxyl radicals generated during aerobic metabolism, are inactivated or scavenged by antioxidants before they can cause damage to lipids, proteins, or nucleic acids [40].…”

“…CAT enzyme plays crucial roles as antioxidants and constitutes the primary defense system against the toxic effects of superoxide radicals (O2−) in organisms [40]. According to the most acceptable free radical theory of aging, the potentially toxic-free radicals, primarily the ROS, superoxide, and hydroxyl radicals generated during aerobic metabolism, are inactivated or scavenged by antioxidants before they can cause damage to lipids, proteins, or nucleic acids [40]. To test this hypothesis, the Drosophila fly protein samples of each experimental condition were tested for SOD and CAT activities.…”

Queuosine Deficiency in Eukaryotes Compromises Tyrosine Production through Increased Tetrahydrobiopterin Oxidation

“…Previous reports suggest that queuine can enhance the phosphorylation of unspecified cytosolic proteins (22), whereas in other cases a decrease in phosphorylation was observed (33)(34)(35). In addition, notable similarities exist between the structure of queuine and tetrahydrobiopterin, both being derived from GTP.…”

Lost in Translation: Defects in Transfer RNA Modifications and Neurological Disorders

“…This suggests that queuine, the Q precursor is an essential micronutrient and also plays an important role in biosynthesis of Q to form Q-tRNA (Nishimura, 1983; Kersten, 1988). Queuine has been shown to promote the activity of antioxidant enzymes and thus may have a role in improving the antioxidant defense system (Pathak et al, 2008). Queuine has been shown to induce cell differentiation in cancerous cells (Chen and Wu, 1994).…”