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Arylamine activating sulfotransferase in liver
K Nagata1, K Yoshinari, S Ozawa
1Division of Drug Metabolism and Molecular Toxicology, Faculty of Pharmaceutical Sciences, Tohoku University, Sendai, Japan.
Abstract:
Carcinogenic N-hydroxy-arylamines and -arylamides undergo metabolic activation by several enzymes in mammals to cause the DNA damage. Cytosolic sulfotransferases in rat and human livers, which belong to the ST1 (SULT1) family, have been studied to assess their properties to mediate the metabolic activation. A human orthologue of rat ST1C1 from, which catalyzes sulfation of N-hydroxy-2-acetylaminofluorene, was screened in a EMBL genomic library with ST1C1 cDNA [Nagata, K., S. Ozawa, M. Miyata, M. Shimada, D.-W. Gong, Y. Yamazoe and R. Kato (1993) J. Biol. Chem., 268, 24720-24725]. Sequencing of the hybridized clones indicate that at least 3'-terminal region of human ST1C1 orthologue contains sequence highly homologus to rat ST1C1 at both nucleotide and deduced amino acid levels. The experiments using anti-rat ST1C1 antibody and nucleotide probes for human ST1C1 showed no detectable band in Western blots and an mRNA-detecting method with polymerase chain reaction, respectively, in human liver samples.
Insights
Researchers investigated the role of sulfotransferases (SULT1) in activating carcinogenic N-hydroxy-arylamines. They identified a human gene similar to rat ST1C1 but found no detectable expression in human liver samples, suggesting it may not mediate this activation pathway.
Area of Science:
- Biochemistry
- Molecular Biology
- Toxicology
Background:
- Carcinogenic N-hydroxy-arylamines and -arylamides are activated by mammalian enzymes, leading to DNA damage.
- Cytosolic sulfotransferases (SULT1) in rat and human livers are implicated in this metabolic activation process.
Purpose of the Study:
- To identify and characterize a human orthologue of rat ST1C1, an enzyme involved in arylamine metabolic activation.
- To assess the expression and potential role of the human ST1C1 orthologue in human liver.
Main Methods:
- Screening of an EMBL genomic library using rat ST1C1 cDNA to identify homologous human sequences.
- Sequencing of hybridized clones to determine nucleotide and amino acid homology.
- Western blot analysis using anti-rat ST1C1 antibody and RT-PCR with human ST1C1 probes to detect protein and mRNA in human liver samples.
Main Results:
- A human gene with high sequence homology to rat ST1C1 was identified in the 3'-terminal region.
- No detectable protein band for the human ST1C1 orthologue was observed in Western blots of human liver samples.
- No detectable mRNA for the human ST1C1 orthologue was found in human liver samples using RT-PCR.
Conclusions:
- The identified human ST1C1 orthologue shows significant sequence similarity to its rat counterpart.
- Despite sequence homology, the human ST1C1 orthologue does not appear to be expressed in human liver, suggesting it may not play a significant role in the metabolic activation of N-hydroxy-arylamines in this tissue.