Characterization of a novel silkworm (Bombyx mori) phenol UDP‐glucosyltransferase

Abstract

Sugar conjugation is a major pathway for the inactivation and excretion of both endogenous and exogenous compounds. We report here the molecular cloning and functional characterization of a phenol UDP-glucosyltransferase (UGT) from the silkworm, Bombyx mori, which was named BmUGT1. The complete cDNA clone is 1.6 kb, and the gene is expressed in several tissues of fifth-instar larvae, including fat body, midgut, integument, testis, silk gland and haemocytes. The predicted protein comprises 520 amino acids and has 30% overall amino-acid identity with other members of the UGT family. The most conserved region of the protein is the C-terminal half, which has been implicated in binding the UDP-sugar. BmUGT1 was expressed in insect cells using the baculovirus expression system, and a range of compounds belonging to diverse chemical groups were assessed as potential substrates for the enzyme. The expressed enzyme had a wide substrate specificity, showing activity with flavonoids, coumarins, terpenoids and simple phenols. These results support a role for the enzyme in detoxication processes, such as minimizing the harmful effects of ingested plant allelochemicals. This work represents the first instance where an insect ugt gene has been associated with a specific enzyme activity.

A silkworm–baculovirus model for assessing the therapeutic effects of antiviral compounds: characterization and application to the isolation of antivirals from traditional medicines

“…We demonstrated that antibiotics used clinically to treat infected humans are effective in silkworms, and that the ED 50 values of the antibiotics used in the silkworm infection model are consistent with those obtained in mammalian animal models (Hamamoto et al, 2004(Hamamoto et al, , 2005Hamamoto & Sekimizu, 2005;Kaito et al, 2002Kaito et al, , 2005. Silkworms have enzymes, P450s and conjugating enzymes (Hamamoto et al, 2005;Li et al, 2005;Luque et al, 2002) that are involved in metabolizing antibiotics. Silkworms are large enough for antiviral agents to be injected into their midgut and haemolymph by using syringes.…”

Species-Specific Glucosylation of DIMBOA in Larvae of the Rice Armyworm

“…1) In fact, most of the compounds studied as substrates for insect glucosyltransferases have been plant and synthetic phenolics. [26][27][28] In Drosophila melanogaster, variations in the UDP-glucosyltransferase activity have been analyzed by using the xenobiotic compounds, 1-naphtol and 2-naphtol. 29) In this study, however, we showed that M. separata larvae were able to transform such Bxs such as DIMBOA, HMBOA and MBOA to O-glucosides and methoxy glucoside carbamate as detoxification products.…”

Acidic cellular microenvironment modifies carcinogen-induced DNA damage and repair

“…Moreover, also UDP-glucuronosyltransferase (UGTs) isozymes, which are important phase II enzymes for detoxification of B[a]P metabolites, exhibit a broad pH range from 5.5 to 8.5 in which they can function (Basu et al 2004). The UGTs superfamily is large, and therefore, UGT’s are active over a very wide pH range, and each UGT has its own optimal pH (Luque et al 2002). Since B[a]P metabolizing enzymes have different relative activities at different pH, it can be expected that B[a]P metabolism is significantly affected by pH.…”