Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.6.1.44 (AGT)
770 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Heterozygous missense mutation in codon 15 of the rhodopsin gene was detected in a patient with autosomal dominant retinitis pigmentosa (ADRP), where a transition of adenine to guanine at the second nucleotide in codon 15 (AAT-->AGT), corresponding to a substitution of serine residue for asparagine residue (Asn-15-Ser) was detected. None of the remaining unrelated 42 ADRP, 24 autosomal recessive RP (ARRP) and 34 normal individuals had this alteration. Her funduscopic findings were sectorial in type similar to that of the patients with the same mutation found in an Australian pedigree (Sullivan et al., 1993). This study shows phenotypic similarities in patients with the same mutation of a different ancestry.
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PMID:Missense mutation of rhodopsin gene codon 15 found in Japanese autosomal dominant retinitis pigmentosa. 852 2

Serine:pyruvate/alanine:glyoxylate aminotransferase (SPT/AGT) of rat liver is localized in both mitochondria and peroxisomes. The rat SPT/AGT gene is single, but there are two species of mRNA which differ at their 5' termini due to transcription from two alternative initiation sites. The longer mRNA is translated from the first AUG codon and thereby directs synthesis of the 45 kDa precursor of mitochondrial SPT/AGT, which includes a mitochondria-targeting N-terminal signal sequence. Peroxisomal SPT/AGT is synthesized as a product of mature size (43 kDa) from the shorter mRNA, which starts 3' to the first AUG codon and thus is translated from a downstream AUG codon. In our previous immunocytochemical study, SPT/AGT was found to be localized only in peroxisomes, when a cDNA encoding 43 kDa SPT/AGT was expressed in COS cells. When a cDNA encoding the 45 kDa precursor was expressed, on the other hand, SPT/AGT was localized mostly in mitochondria, but a small number of peroxisomes were also positively stained [Yokota, S., Funai, T., and Ichiyama, A. (1991) Biomed. Res. 12, 53-59]. We show in this paper that 43 kDa SPT/AGT is also synthesized from the longer mRNA in an in vitro translation system through a leaky scanning mechanism. Although the first AUG initiator codon is in a suboptimal context, the amount of 43 kDa SPT/AGT synthesized from the longer mRNA was small, probably because a downstream stem-loop structure facilitates recognition of the first AUG initiator codon.
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PMID:Fidelity of translation initiation of mRNA for the precursor of rat mitochondrial serine:pyruvate/alanine:glyoxylate aminotransferase. 858 12

Male pseudohermaphroditism due to 5 alpha-reductase deficiency was clinically and biochemically described in a large Dominican kindred of 23 families with 38 affected subjects in 1974. Recently, the 5 alpha-reductase-2 gene defect in the large Dominican kindred was found to be due to a single base substitution of thymidine (TGG) for cytosine (CGG) on exon 5 of the 5 alpha-reductase-2 gene, causing a tryptophan replacement of arginine at amino acid 246 (R246W) of the enzyme. In the present report, affected subjects from four additional Dominican families were studied to determine whether they carried the same 5 alpha-reductase-2 gene defect as the large kindred, suggesting a common ancestry for the gene defect within this small country. Using single strand conformational polymorphism and DNA sequencing, two other mutations of the 5 alpha-reductase-2 gene were found in affected subjects from two of the four families. A point mutation on exon 2 of the 5 alpha-reductase-2 gene, in which substitution of adenine (GAC) for guanine (GGC) caused an aspartic acid replacement of glycine at amino acid 115 (G115D), was demonstrated in one of these families, and a substitution of adenine (AGT) for guanine (GGT) on exon 3 causing a serine replacement for glycine at amino acid 183 (G183S) was detected in the other family. Affected subjects from the two remaining families demonstrated the same exon 5 mutation of the 5 alpha-reductase-2 gene as previously detected in the large Dominican kindred. The phenotypic and biochemical characteristics of the male pseudohermaphrodites were similar regardless of the genetic defect, except that one affected subject (C-VI-2) with the same exon 5 mutation as the large Dominican kindred had much more facial and body hair. Thus, the identification of multiple mutations in the 5 alpha-reductase-2 gene in male pseudohermaphrodites from the Dominican Republic demonstrates a lack of common ancestry, as had been previously postulated.
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PMID:5 alpha-reductase-2 gene mutations in the Dominican Republic. 862 25

Mutations in distinct sites of epidermal keratins, in particular in the helix initiation and termination regions, cause human genodermatoses due to faulty intermediate filament formation. Extension of this observation to human hereditary hair and nail diseases includes population analyses of human hair keratin genes for natural sequence variations in the corresponding sites. Here we report on a large-scale genotyping of the short helix termination region (HTR) of the human type I cortical hair keratins hHa1, a3-I, and a3-II, and the cuticular hair keratin hHa2. We describe two polymorphic loci, P1 and P2, exclusively in the cuticular hHa2 gene, both creating dimorphic protein variants. P1 is due to a C to T mutation in a CpG element leading to a threonine to methionine substitution; P2 concerns a serine codon AGT that also occurs as an asparagine coding variant AAC. A third polymorphism, P3, is linked with a C to T point mutation located at the very beginning of intron 6. The three polymorphic sites are clustered in a 39-nucleotide sequence of the hHa2 gene. Both allelic frequency calculations in individuals of different races and pedigree studies indicate that the two-allelic hHa2 variants resulting from P1 and P2 occur ubiquitously in a ratio of about 1:1 (P1) and 2:1 (P2) respectively in our survey, and are clearly inherited as Mendelian traits. A genotype carrying both mutations simultaneously on one allele could not be detected in our sampling, and there was no association of a distinct allelic hHa2 variant with the known ethnic form variations of hairs. Sequence comparisons of the HTR of hHa2 with those of other type I hair keratins including the hHa2-ortholog from chimpanzee provide evidence that the P1- and P2-linked mutations must have occurred very early in human evolution and that the two P2-associated codon variants may be the result of two independent point mutations in an ancestral AGC serine codon. These data describe natural polymorphisms in the HTR of a member of the keratin multigene family.
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PMID:The region coding for the helix termination motif and the adjacent intron 6 of the human type I hair keratin gene hHa2 contains three natural, closely spaced polymorphic sites. 864 91

A subset of human growth hormone (GH)-secreting pituitary tumors contains the gsp oncogene that encodes an activation mutation of the alpha-subunit of the stimulatory GTP-binding protein (G(S) alpha). This study was undertaken to investigate the frequency of the gsp oncogene in GH-secreting pituitary tumors in Korean acromegalic patients and to elucidate the clinical characteristics of these patients to endocrine testing. Direct polymerase chain reaction sequencing revealed the gsp oncogene mutation in 9 out of 21 tumors (43%) at amino acid 201 of the G(S) alpha protein. A single nucleotide mutation in the tumors carrying the gsp oncogene was observed, which replaced an arginine (CGT) in the normal protein with cysteine (TGT) in eight tumors and serine (AGT) in one tumor. The patients with the gsp oncogene mutation (group 1) were older (54 +/- 10 vs 41 +/- 11 years, p = 0.0085) than those without the mutation (group 2). Sex, tumor size and grade, basal GH and prolactin levels, the GH response to oral glucose loading, the GH fluctuation and the paradoxical response to thyrotropin-releasing hormone or gonadotropin-releasing hormone did not differ between the groups. The gsp oncogene was found mostly in somatotroph adenomas. The octreotide-induced GH suppression was significantly higher in group 1 than in group 2 (95 +/- 5% vs 81 +/- 17%, p = 0.0335). The GH response to bromocriptine did not differ between the groups. These results suggest that the G(S) alpha mutations of GH-secreting tumor are observed in Korean acromegalic patients with similar frequency to those of western countries. The patients with gsp oncogene are likely to be older than those without the oncogene, and show excellent response of GH suppression to octreotide.
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PMID:Characteristics of gsp-positive growth hormone-secreting pituitary tumors in Korean acromegalic patients. 876 42

The gene encoding serine-glyoxylate aminotransferase, one of key enzymes for the assimilation of one-carbon compounds in methylotrophs, and its flanking regions were isolated from an obligate methylotrophic bacterium, Hyphomicrobium methylovorum GM2. Nucleotide sequencing of the recombinant plasmids revealed that the serine-glyoxylate aminotransferase gene encodes a 405-amino-acid protein with a calculated molecular mass of 43880 Da. The amino acid sequence of the enzyme showed identity to the sequences of serine-glyoxylate aminotransferase of Methylobacterium extorquens AM1 (57%), aspartate aminotransferase of Methanobacterium thermoformicicum (31%), human peroxisomal alanine-glyoxylate aminotransferase (27%), and serine-pyruvate aminotransferase of rat liver mitochondria (33%). The recombinant plasmid, which was constructed by ligation of the cloned gene and an expression vector pKK223-3, was introduced into Escherichia coli HB101. The recombinant enzyme was purified from transformed E. coli cells and analyzed by immunological and enzymological methods. The overexpressed enzyme was indistinguishable from the wild-type enzyme isolated from H. methylovorum GM2.
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PMID:Cloning and expression of the gene for serine-glyoxylate aminotransferase from an obligate methylotroph Hyphomicrobium methylovorum GM2. 889 80

In rat liver, a single serine:pyruvate/alanine:glyoxylate aminotransferase (SPT or SPT/AGT) gene is transcribed from two transcription initiation sites. Transcription from the upstream site generates the mRNA encoding the precursor for mitochondrial SPT (pSPTm) and is markedly enhanced by the administration of glucagon or cAMP. In this report we show the increase in the downstream transcript, the peroxisomal SPT (SPTp) mRNA, caused by peroxisome proliferators and triiodothyronine (T3). In the case of T3, the pSPTm mRNA was also increased 72 h after a single administration of the hormone in addition to an earlier increase in SPTp mRNA.
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PMID:Induction by peroxisome proliferators and triiodothyronine of serine:pyruvate/alanine:glyoxylate aminotransferase of rat liver. 942 25

Isozymes of 17beta-hydroxysteroid dehydrogenase (17betaHSD) regulate levels of bioactive androgens and estrogens in a variety of tissues. For example, the 17betaHSD type 3 isozyme catalyzes the conversion of the inactive C19-steroid androstenedione to the biologically active androgen, testosterone, in the testis. Testosterone is essential for the correct development of male internal and external genitalia; hence, deleterious mutations in the HSD17B3 gene give rise to a rare form of male pseudohermaphroditism termed 17betaHSD deficiency. Here, 2 additional missense mutations in the HSD17B3 gene in subjects with 17betaHSD deficiency are described. One mutation (A56T) impairs enzyme function by affecting NADPH cofactor binding. A second mutation (N130S) led to complete loss of enzyme activity. Also, a single base pair polymorphism in exon 11 of the HSD17B3 gene is described. The polymorphic A allele encodes a protein with a serine rather than a glycine at position 289 (GGT --> AGT). The frequency of the G allele (Gly) was 0.94, and that of the A allele (Ser) was 0.06. No difference in the frequencies of the G and A alleles was detected in 32 apparently normal women and 46 women with polycystic ovary syndrome. Enzymes bearing either glycine or serine at this position have similar substrate specificities and kinetic constants. The current findings boost to 16 the number of mutations in the HSD17B3 gene that impair testosterone synthesis and cause male pseudohermaphroditism, and add 1 apparently silent polymorphism to this tally.
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PMID:Deleterious missense mutations and silent polymorphism in the human 17beta-hydroxysteroid dehydrogenase 3 gene (HSD17B3). 970 59

The accumulation of mutant p53 protein in cancer cells was observed by immunohistochemistry analysis. DNA was extracted from paraffin-embedded tissue. Exons 5, 7 and 8 were amplified and studied by PCR-SSCP and sequencing analysis. Ten cases of asbestos associated cancer tissue were studied, of which five cases had adenocarcinoma, and the other five had mesothelioma, squamous carcinoma, small cell lung cancer, adenosquamous carcinoma and malignant lymphoma respectively. Employing monoclonal antibody PAb1801, five cases were found to be mutant p53 protein positive. Seven cases were found to have mutations by PCR-SSCP. A total of 7 cases (8 mutations) were found to be positive and 4 cases were found to be positive by both of these analyses. Of the 8 mutations found by SSCP analysis, 4(50%, 4/8) were clustered in exon 8. A high mutation frequency was noticed in adenocarcinoma (80%, 4/5). Sequencing analysis on two specimens revealed two hotspot mutations. In codon 234, TAC for tyrosin was mutated to AAC for asparagine by a T to A transversion of the first letter. In codon 273, CGT for arginine was mutated to AGT for serine by a C to A transversion of the first letter. In conclusion, the mutation of p53 gene is common in asbestos associated cancers. However, the mutational spectrum of asbestos associated cancers might be different from that of non-asbestos associated cancers.
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PMID:p53 gene mutations in asbestos associated cancers. 986 81

L-Serine metabolism in rat liver was investigated, focusing on the relative contributions of the three pathways, one initiated by L-serine dehydratase (SDH), another by serine:pyruvate/alanine:glyoxylate aminotransferase (SPT/AGT), and the other involving serine hydroxymethyltransferase and the mitochondrial glycine cleavage enzyme system (GCS). Because serine hydroxymethyltransferase is responsible for the interconversion between serine and glycine, SDH, SPT/AGT, and GCS were considered to be the metabolic exits of the serine-glycine pool. In vitro, flux through SDH was predominant in both 24-h starved and glucagon-treated rats. Flux through SPT/AGT was enhanced by glucagon administration, but even after the induction, its contribution under quasi-physiological conditions (1 mM L-serine and 0.25 mM pyruvate) was about (1)/(10) of that through SDH. Flux through GCS accounted for only several percent of the amount of L-serine metabolized. Relative contributions of SDH and SPT/AGT to gluconeogenesis from L-serine were evaluated in vivo based on the principle that 3H at the 3 position of L-serine is mostly removed in the SDH pathway, whereas it is largely retained in the SPT/AGT pathway. The results showed that SPT/AGT contributed only 10-20% even after the enhancement of its activity by glucagon. These results suggested that SDH is the major metabolic exit of L-serine in rat liver.
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PMID:Flux of the L-serine metabolism in rat liver. The predominant contribution of serine dehydratase. 1034 51


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