Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: HUMANGGP:011460 (HLUG25)
 5 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Two human liver UDP-glucuronosyltransferase cDNA clones, HLUG25 [Jackson, M. R., et al. (1987) Biochem. J. 242, 581-588] and UDPGTh-2 [Ritter, J. K., et al. (1990) J. Biol. Chem. 266, 7900-7906] have previously been shown to encode isozymes active in the glucuronidation of hyodeoxycholic acid (HDCA) and certain estrogen derivatives (estriols and 3,4-catechol estrogens), respectively. Here we report that the UDPGTh-2-encoded isoform (udpgth-2) and the HLUG25-encoded isoform (udpgth-1) have parallel aglycon specificities. Following expression in COS-1 cells, each isoform metabolized three types of dihydroxy- or trihydroxy-substituted ring structures, including the 3,4-catechol estrogen (4-hydroxyestrone), estriol and 17-epiestriol, and HDCA, but the udpgth-2 isozyme is 100-fold more efficient than udpgth-1. udpgth-1 and udpgth-2 are 86% identical overall (76 differences out of 528 amino acids), including 55 differences in the first 300 amino acids of the amino terminus, a domain which confers isoform substrate specificity. The data indicate that a high level of conservation in the amino terminus is not required for the preservation of substrate selectivity. Analysis of glucuronidation activity encoded by UDPGTh-1/UDPGTh-2 chimeric cDNAs constructed at their common restriction sites, SacI (codon 297), NcoI (codon 385), and HhaI (codon 469), showed that nine amino acids between residues 385 and 469 are important for catalytic efficiency, suggesting that this region represents a domain which is critical for catalysis but distinct from that responsible for aglycon selection.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Two human liver cDNAs encode UDP-glucuronosyltransferases with 2 log differences in activity toward parallel substrates including hyodeoxycholic acid and certain estrogen derivatives. 155 22

Two human liver UDP-glucuronosyltransferase cDNA clones (HLUGP1 and HLUG25) were individually inserted into the eukaryotic expression vector pKCRH2. Each recombinant plasmid was cotransfected with a SFVneo vector, thereby allowing establishment of several V79 cell lines retaining the exogenous UDP-glucuronosyltransferase cDNA after selection with G418 (Geneticin). Southern blot analysis suggested that the cDNAs were integrated into the host cell genome. Northern blot and immunoblot analyses indicated that the cDNAs were correctly transcribed and translated for the production of functional enzymes. The established recombinant V79 cell lines stably expressed the UDP-glucuronosyltransferase activities towards 1-naphthol (HLUGP1) and hyodeoxycholic acid (HLUG25) at levels 10-20-fold higher than with transient expression, and in the range found in human liver. These high levels of expression of UDP-glucuronosyltransferase activity allowed the determination of apparent kinetic constants and substrate specificities of glucuronidation in the genetically engineered cell lines. HLUG25 cDNA encoded an isoform with restricted specificity towards the 6-OH group of the bile acid hyodeoxycholic acid. The other steroids, bile acids, endobiotics, and xenobiotics tested as substrates were glucuronidated in various samples of human liver microsomes, but not by this isoenzyme. This study, allowing the expression of individual UDP-glucuronosyltransferases in heterologous cells with no endogenous transferases, offered a unique solution for the characterization of UDP-glucuronosyltransferase functional heterogeneity.
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PMID:Stable expression of two human UDP-glucuronosyltransferase cDNAs in V79 cell cultures. 184 92

Two human liver UDP-glucuronosyltransferase cDNA clones, HLUG25 and UDPGTh2 were previously shown to encode isozymes active in the glucuronidation of hyodeoxycholic acid (HDCA) and certain estrogen derivatives (e.g., estriol and 3,4-catechol estrogens), respectively. In this study we have found that the UDPGTh-2-encoded isoform (UDPGTh2) and HLUG25-encoded isoform (UDPGTh1) have parallel aglycone specificities. When expressed in COS 1 cells, each isoform metabolized three types of dihydroxy- or trihydroxy-substituted ring structures, including the 3,4-catechol estrogen (4-hydroxyestrone), estriol, 17-epiestriol, and HDCA, but the UDPGTh2 isozyme was 100-fold more efficient than UDPGTh1. UDPGTh1 and UDPGTh2 were 86% identical overall (76 differences out of 528 amino acids), including 55 differences in the first 300 amino acids of the amino terminus, a domain which conferred the substrate specificity. The data indicated that a high level of conservation in the amino terminus was not required for the preservation of substrate selectivity. Analysis of glucuronidation activity encoded by UDPGTh1/UDPGTh2 chimeric cDNA constructed at their common restriction sites,Sac 1 (codon 297),Nco 1 (codon 385), andHha 1 (codon 469), showed that nine amino acids between residues 385 and 469 were important for catalytic efficiency, suggesting that this region represented a domain which was critical for the catalysis but distinct from that responsible for aglycone selection. These data indicate, that UDPGTh2 is a primary isoform responsible for the detoxification of the bile salt intermediate as well as the active estrogen intermediates.
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PMID:Comparison of glucuronidating activity of two human cDNAs, UDPGTh1 and UDPGTh2. 1898 89