Characterization of a cloned human dihydrotestosterone/androstanediol UDP-glucuronosyltransferase and its comparison to other steroid isoforms.
A human cDNA, UDPGTh-3, encoding a dihydrotestosterone/5 alpha-androstane-3 alpha,17 beta-diol UDP- glucuronosyltransferase (transferase) has been isolated and characterized. The nucleotide sequence of UDPGTh-3 encodes a 530 amino acid protein with a typical membrane insertion-signal peptide, a membrane-anchoring domain, and three potential asparagine-linked glycosylation sites. Alignment shows that this encoded isozyme is 96% identical to an apparent estriol-metabolizing isoform, HLUG4 [Coffman, B. L., et al., (1990) Arch. Biochem. Biophys. 281, 170-175]. The udpgth-3 isozyme is 78% identical to two other steroid isoforms, HLUG25 (udpgth-1) [Jackson, M. R., et al. (1987) Biochem. J. 242, 581-588; Ritter, J. K., et. al. (1992) Biochemistry 31, 3409-3414] and udpgth-2 [Ritter, J. K., et al. (1990) J. Biol. Chem. 265, 7900-7906]. udpgth-2 and udpgth-1 metabolized parallel substrates (stereospecific estriols, 3,4-catechol estrogens, and the bile salt hyodeoxycholate), except that udpgth-2 was 100-fold more effective than udpgth-1. The mRNA encoding udpgth-3 is 2.4 kb in size and is present in liver, prostate, and testis; the mRNA encoding udpgth-2 is located in liver and kidney, whereas that for udpgth-1 is liver-specific. Each of the liver mRNA species encoding udpgth-3, udpgth-2, or udpgth-1 was induced 2.5-3-fold by phenobarbital treatment of the Erythrocebus patas monkey. In 16 human liver mRNA samples, the message encoding udpgth-3 was generally uniformly expressed and that for udpgth-1 exhibited wide variations in its level, whereas that for udpgth-2 was barely detectable in nine samples and not detectable in the others. Three samples contained no message for either isoform. Substrate turnover by udpgth-3 is ranked as follows: phenolphthalein > 5 alpha-androstane-3 alpha,17 beta-diol > 5 alpha- dihydrotestosterone = 4-hydroxybiphenyl > phenolsulfonphthalein (phenol red) > phenolphthalin. Genes encoding udpgth-3, udpgth-2, and udpgth-1 mapped to human chromosome 4 with genomic DNA from human/mouse and human/hamster somatic cell hybrids; the genes encoding udpgth-1 and udpgth-2 mapped specifically to band 4q28. udpgth-3 exhibited similar Km values both for 5 alpha-dihydrotestosterone (10 microM) and for its metabolite, 5 alpha-androstane-3 alpha,-17 beta-diol (12.5 microM).(ABSTRACT TRUNCATED AT 400 WORDS)
Chen
F
F
Section on Genetic Disorders of Drug Metabolism, National Institute of Child Health and Human Development.
Ritter
J K
JK
Wang
M G
MG
McBride
O W
OW
Lubet
R A
RA
Owens
I S
IS
D000595:Amino Acid Sequence; D000818:Animals; D015152:Blotting, Northern; D002874:Chromosome Mapping; D002894:Chromosomes, Human, Pair 4; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000378:metabolism; D004901:Erythrocebus patas; D014453:Glucuronosyltransferase / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007527:Isoenzymes / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008297:Male; D008969:Molecular Sequence Data; D009928:Organ Specificity; D011467:Prostate / Q000201:enzymology; D012333:RNA, Messenger / Q000032:analysis / Q000096:biosynthesis; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D013737:Testis / Q000201:enzymology
D018076:DNA, Complementary; D007527:Isoenzymes; D012333:RNA, Messenger; D011994:Recombinant Proteins; D014453:Glucuronosyltransferase