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PubMed2001

GABA-transaminase, the liver and infantile autism.

Gamma-aminobutyric acid (GABA) is a major inhibitory neurotransmitter of the mammalian brain and the enzyme responsible for catabolism (breakdown in the liver during regulation) is GABA-Transaminase (GABA-T). Recently, Cohen has shown that extremely high GABA levels in the urine and blood were observed for an autistic child. The finding that elevated levels of GABA in the urine and blood are present for an autistic child could explain why autistic features (such as self-stimulatory behavior and language delays, etc.) are found. Increasing the GABA-T enzyme activity for this autistic patient could result in less plasma GABA (after liver regulation) entering into the bloodsteam and brain and it is postulated that this could result in a reduction of the autistic features (such as self-stimulatory behavior and language delays, etc.) due to abnormal development of the axon(s) in the corpus callosum.

4-Aminobutyrate Transaminase↗
PubMed1980

Changes in alanine transaminase activity in several organs of the rat induced by a 24-hour fast.

The activity of alanine transaminase in the liver, intestine, stomach, striated muscle, kidneys, adipose tissue, brain and skin of fed and 24-hours fasted adult rats has been determined. The range of activities expressed per unit of protein and DNA weight is rather similar in most organs, with highest values for the liver enzyme. Fasting induced significant increases mainly in peripheral organs, with a combined 35% increase, whereas the liver capability actually decreased by 14% because of the decrease in liver size; and all other splanchnic extrahepatic tissues activity studied increased by 22%. The results obtained agree with the postulated activity of the glucose-alanine cycle under these conditions of fasting.

Alanine Transaminase↗
PubMed1980

Cerebral metabolism following brain injury, III. Transaminase changes.

Glutamic oxalacetic and glutamic pyruvic transaminase levels in CSF and blood were estimated in 25 normal individuals and 50 patients with varying grades of head injury. CSF GOT, and to a lesser extent GPT, showed significant elevation proportionate to the degree of brain injury. Serum GOT was raised in more severe injuries. CSF GOT and GPT levels showed a significant correlation with the prognosis of the case.

Alanine Transaminase↗
PubMed1980

[Transaminase increase: a largely unknown side-effect of heparin treatment (author's transl)].

GOT, GPT and some other enzyme levels were measured systematically in 46 patients receiving subcutaneous heparin treatment. The heparin dosage varied between 5,000 and 15,000 IU, given every eight hours. During heparinisation a rise in GPT (average maximal values 67.0 +/- 7.3 U/l on the eighth treatment day) occurred in 89% of patients, while a rise in GOT (mean maximal values 39.7 +/- 3.9 U/l on the fifth treatment day) occurred in 82%. On reaching maximal value, enzyme activity decreased to the initial value despite continuing heparin treatment. A certain dependence of the incidence and (or) extent of the transaminase increase on heparin dosage was noted, especially comparing low-dose and full heparinisation. An increase in gamma-GT during subcutaneous heparinisation occurred in 37% of patients, while there was no significant change in alkaline phosphatase and lactate dehydrogenase.

Adolescent↗
PubMed2006

Crystal structure of the Anopheles gambiae 3-hydroxykynurenine transaminase.

In Anopheles gambiae, the vector for the most deadly malaria parasite Plasmodium falciparum, xanthurenic acid (XA) plays a key role in parasite gametogenesis and fertility. In mosquitoes, XA is produced by transamination of 3-hydroxykynurenine (3-HK), a reaction that represents the main route to prevent the accumulation of the potentially toxic 3-HK excess. Interfering with XA metabolism in A. gambiae therefore appears an attractive avenue for the development of malaria transmission-blocking drugs and insecticides. We have determined the crystal structure of A. gambiae 3-HK transaminase in its pyridoxal 5'-phosphate form and in complex with a newly synthesized competitive enzyme inhibitor. Structural inspection of the enzyme active site reveals the key molecular determinants for ligand recognition and catalysis. Major contributions toward inhibitor binding are provided by a salt bridge between the inhibitor carboxylate and Arg-356 and by a remarkable hydrogen bond network involving the anthranilic moiety of the inhibitor and backbone atoms of residues Gly-25 and Asn-44. This study may be useful for the structure-based design of specific enzyme inhibitors of potential interest as antimalarial agents.

Animals↗
PubMed1969

Daily rhythms in hepatic polysome profiles and tyrosine transaminase activity: role of dietary protein.

Hepatic polysome profiles vary in untreated rats as a function of time of day. The ratio of polysomes to total ribosomes increases from 50 to 73 per cent in darkness. There is also a daily rhythm in tyrosine transaminase activity which resembles but does not coincide with the polysome rhythm. Both rhythms are dependent on the cyclic ingestion of dietary protein, and disappear in rats given a protein-free diet.

Animals↗
PubMed1996

Mitochondrial and cytosolic branched-chain amino acid transaminases from yeast, homologs of the myc oncogene-regulated Eca39 protein.

We have isolated a high copy suppressor of a temperature-sensitive mutation in ATM1, which codes for an ABC transporter of Saccharomyces cerevisiae mitochondria. The suppressor, termed BAT1, encodes a protein of 393 amino acid residues with an NH2-terminal extension that directs Bat1p to the mitochondrial matrix. A highly homologous protein, Bat2p, of 376 amino acid residues was found in the cytosol. Both Bat proteins show striking similarity to the mammalian protein Eca39, which is one of the few known targets of the myc oncogene. Deletion of a single BAT gene did not impair growth of yeast cells. In contrast, deletion of both genes resulted in an auxotrophy for branched-chain amino acids (Ile, Leu, and Val) and in a severe growth reduction on glucose-containing media, even after supply of these amino acids. Mitochondria and cytosol isolated from bat1 and bat2 deletion mutants, respectively, contained largely reduced activities for the conversion of branched-chain 2-ketoacids to their corresponding amino acids. Thus, the Bat proteins represent the first known isoforms of yeast branched-chain amino acid transaminases. The severe growth defect of the double deletion mutant observed even in the presence of branched-chain amino acids suggests that the Bat proteins, in addition to the supply of these amino acids, perform another important function in the cell.

Amino Acid Sequence↗
PubMed2000

Glc7p protein phosphatase inhibits expression of glutamine-fructose-6-phosphate transaminase from GFA1.

Inhibitor-1 (I-1) is a specific inhibitor of protein phosphatase-1 (PP1). We assayed the ability of I-1 to inhibit Saccharomyces cerevisiae PP1, Glc7p, in vivo. Glc7p like other PP1 catalytic subunits associates with a variety of noncatalytic subunits, and Glc7p holoenzymes perform distinct physiological roles. Our results show that I-1 inhibits Glc7p holoenzymes that regulate transcription and mitosis, but holoenzymes responsible for meiosis and glycogen metabolism were unaffected. Additionally, we exploited a genetic screen for mutants that were dependent on I-1 to grow. This scheme can identify processes that are negatively regulated by Glc7p-catalyzed dephosphorylation. In this paper I-1-dependent gfa1 mutations were analyzed in detail. GFA1 encodes glutamine-fructose-6-phosphate transaminase. One or more phosphorylated proteins activate GFA1 transcription because the pheromone response and Pkc1p/mitogen-activated protein kinase pathways positively regulate GFA1 transcription. Our findings show that an I-1-sensitive Glc7p holoenzyme reduces GFA1 transcription. Therefore, GFA1 is a member of a growing list of genes that are negatively regulated by Glc7p dephosphorylation.

Catalysis↗
PubMed2000

Effects of 1-year interferon-alpha 2a treatment in patients with chronic hepatitis C and persistently normal transaminase activity.

BACKGROUND: Certain chronic hepatitis C carriers have persistently normal transaminase activity. The aims of this study were to determine the virologic and histologic effects of 1 year of interferon-alpha treatment in such patients. METHODS: Thirty-one patients were followed up in our Liver Unit. Eleven accepted interferon-alpha therapy; the 20 others were not treated and served as controls. Interferon-alpha, 3 MU, was given thrice weekly for 1 year. Serum was examined for hepatitis C virus (HCV)-RNA before, at the end of, and 6 months after treatment. Liver biopsy was performed 6 months after the cessation of treatment in 10 of 11 treated patients (one refused biopsy) and after a mean of 30.6+/-22.7 months in the 20 untreated patients. RESULTS: At the end of follow-up two of the treated patients had undetectable serum HCV-RNA and five had increased alanine aminotransferase (ALAT) values. In contrast, only one of the untreated patients had abnormal ALAT activity. All 20 untreated patients were constantly viremic. No significant histologic improvement was observed in the treated patients evaluated by means of post-treatment liver biopsy. The mean annual progression rate of fibrosis was very slow and similar in the treated and untreated patients (0.09 (range, 0-0.62) versus 0.07 (range, 0-0.60) fibrosis units). CONCLUSIONS: One year of interferon-alpha treatment can suppress HCV-RNA in patients with chronic hepatitis C and persistently normal ALAT values followed up over long periods. The rate of fibrosis progression in such patients is very slow, and therapeutic strategies should take this fact into account. Antiviral treatment is debated for patients without fibrosis in initial biopsy specimens.

Adult↗
PubMed2006

Hyperalbuminemia and elevated transaminases associated with high-protein diet.

While high protein diets are increasing in popularity, there is a lack of data on their potential adverse effects. We describe two patients on high protein supplements and exercising for physical fitness. Both developed intermittent abdominal pain, transient elevations in transaminases and hyperalbuminemia without there being any identifiable cause. The symptoms and abnormalities on the laboratory tests resolved after the high protein intake was discontinued. While the pathogenesis and importance of these abnormalities need further study, the findings raise concerns regarding the safety of high protein diets combined with high intensity exercise.

Adult↗
PubMed2002

Factors associated with mortality in human immunodeficiency virus type 1-infected adults initiating protease inhibitor-containing therapy: role of education level and of early transaminase level elevation (APROCO-ANRS EP11 study). The Antiprotéases Cohorte Agence Nationale de Recherches sur le SIDA EP 11 study.

This study attempted to identify factors associated with mortality among human immunodeficiency virus (HIV)-infected adults starting a protease inhibitor (PI)-containing therapy. Among 1155 patients consecutively enrolled in the APROCO study between May 1997 and June 1998, clinical characteristics were as follows: median age, 36 years; median baseline CD4 cell count, 288 cells/mm(3); and median baseline plasma HIV RNA load, 4.4 log(10) copies/mL. After a median follow-up of 27 months, 48 deaths had occurred, of which 44% were related to acquired immune deficiency syndrome. The mortality rate was 2.9% at 12 months. When both data at baseline and data at 4 months after the start of PI therapy were considered, factors independently associated with mortality were (Cox model) low baseline plasma creatinine level, low school education level, low CD4 cell count at 4 months, low hemoglobin level, and elevated hepatic transaminase levels. Thus, social context plus clinical and biologic data, including the 4-month response to treatment, must be considered in treatment of HIV-infected patients.

Antiretroviral Therapy, Highly Active↗
PubMed1989

Genetic polymorphism of glutamate-pyruvate transaminase (alanine aminotransaminase): influence on erythrocyte activity as a marker of vitamin B-6 nutritional status.

A new, sensitive, two-step method free from interference by hemoglobin that measures erythrocyte glutamate-pyruvate transaminase (E-GPT) activity is described. Several aspects of E-GPT activity as an index of vitamin B-6 nutritional status were investigated with this method. 1) GPT shows a structural genetic polymorphism with two common alleles resulting in three phenotypes. In a population study (n = 92) E-GPT activity differed significantly (p less than 0.001) among the three phenotypic groups. Plasma pyridoxal-5'-phosphate concentrations in the three groups did not differ significantly. Therefore, E-GPT activity can only be used to assess vitamin B-6 nutritional status if GPT phenotype is accounted for. 2) Pyridoxine supplementation (10 mg/d) significantly (p less than 0.0001) increased E-GPT activity and decreased (p less than 0.0001) the percentage stimulation by pyridoxal-5'-phosphate in vitro although the absolute amount of in vitro stimulation by pyridoxal-5'-phosphate changed only marginally. 3) Inorganic phosphate inhibits in vitro activation of E-GPT by pyridoxal-5'-phosphate.

Alanine Transaminase↗
PubMed1978

Hepatic transaminase in protein-restricted rats: development of a controlled model.

A marginal protein malnutrition model which makes allowances for the increasing nutritional requirements of the growing rat and the effects of dietary manipulation on diurnal rhythms, while still rigidly controlling the level of protein restriction, is reported. A predetermined, constantly increasing intake of four purified diets, providing approximately 40 to 160% of the National Research Council protein requirement for rats was fed to rats receiving a nitrogen-free energy source adlibitum. This standardization reduced within-group variation and allowed precise growth reproducibility. Biochemical parameters were measured at evenly spaced intervals throughout the day to remove diurnal differences from between-group comparisons. Growth, nitrogen balance, and 24-hour means of liver weight, DNA, RNA, protein, and glutamate-oxaloacetate and glutamate-pyruvate transaminases reflected protein intake. However, when growth was depressed 10, 30, or 60%, liver GPT/DNA was depressed 40, 49, or 67%, respectively. Hepatic GPT appears to be a sensitive and accurate indicator of marginal protein malnutrition.

Alanine Transaminase↗
PubMed2006

The female-specific Cs-ACS1G gene of cucumber. A case of gene duplication and recombination between the non-sex-specific 1-aminocyclopropane-1-carboxylate synthase gene and a branched-chain amino acid transaminase gene.

Cucumber (Cucumis sativus L.) is a monoecious plant in which female sex expression (gynoecy) is controlled by the Female (F) locus that can be modified by other sex-determining genes as well as by environmental and hormonal factors. As in many other cucurbits, ethylene is the major plant hormone regulating female sex expression. Previously we isolated the Cs-ACS1 (ACS, 1-aminocyclopropane-1-carboxylate synthase) gene that encodes the rate-limiting enzyme in the ethylene biosynthetic pathway. We proposed that Cs-ACS1 is present in a single copy in monoecious (ffMM) plants whereas gynoecious plants (FFMM) contain an additional copy Cs-ACS1G that was mapped to the F locus. To study the origin of Cs-ACS1G, we cloned and analyzed both the gynoecious-specific Cs-ACS1G gene and the non-sex-specific Cs-ACS1 gene. Our results indicate that Cs-ACS1G is the result of a relatively recent gene duplication and recombination, between Cs-ACS1 and a branched-chain amino acid transaminase (BCAT) gene. Taking into consideration that the Cs-ACS1G gene was mapped to the F locus, we propose that this duplication event gave rise to the F locus and to gynoecious cucumber plants. Computer analysis of the 1 kb region upstream of the transcription initiation site revealed several putative cis-acting regulatory elements that can potentially confer the responsiveness of Cs-ACS1G to developmental and hormonal factors and thereby control female sex determination in cucumber. These findings lead us to a model explaining the action of Cs-ACS1 and Cs-ACS1G in cucumber floral sex determination.

Amino Acid Sequence↗
PubMed2002

Exploring routes to stabilize a cationic pyridoxamine in an artificial transaminase: site-directed mutagenesis versus synthetic cofactors.

Two artificial transaminases were assembled by linking a pyridoxamine derivative within an engineered fatty acid binding protein. The goal of mimicking a native transamination site by stabilizing a cationic pyridoxamine ring system was approached using two different strategies. First, the scaffold of intestinal fatty acid binding protein (IFABP) was tailored by molecular modeling and site-directed mutagenesis to position a carboxylate group close to the pyridine nitrogen of the cofactor. When these IFABP mutants (IFABP-V60C/L38K/E93E and -V60C/E51K/E93E) proved to be unstable, a second approach was explored. By N-methylation of the pyridoxamine, a cationic cofactor was created and tethered to Cys60 of IFABP-V60C/L38K and -V60C/E51K; this latter strategy had the effect of permanently installing a positive charge on the cofactor. These chemogenetic assemblies catalyze the transamination between alpha-ketoglutarate and various amino acids with enantioselectivities of up to 96% ee. The pH profile of the initial rates is bell shaped and similar to native aminotransferases. The k(cat) values and the turnover numbers for these new constructs are the highest achieved to date in our system. This success was only made possible by the unique flexibility of the underlying enzyme design concept employed, which permits full control of both the protein scaffold and the catalytically active group.

Amination↗
PubMed2006

Elevated serum alanine transaminase in patients with type 1 or type 2 diabetes mellitus.

BACKGROUND: The risk of chronic liver disease is higher in diabetics, and serum alanine transaminase (ALT) is a sensitive predictor of mortality from liver disease. AIM: To estimate the prevalence of elevated ALT in type 1 and type 2 diabetes, and identify possible risk factors. METHODS: We identified all patients (n = 2077) attending review between September 2002 and August 2003. We excluded those with no ALT measurement (n = 73); those whose alcohol consumption was >14 units/week (women) (n = 276) or >21 units/week (men) (n = 324); and those with a diagnosis of Maturity Onset Diabetes of the Young, secondary diabetes, gestational diabetes or uncertain type of diabetes (n = 51). We calculated the prevalences of elevated ALT in both type 1 and type 2 diabetes patients, and compared the demographic, microvascular risk factors and current drug use between each group using multivariate logistic regression. RESULTS: Of 1353 patients included, 836 (61.9%) had type 2 diabetes. Elevated ALT was found in 9.5% (95%CI 7.1-12.3%) of patients with type 1 diabetes, and 12.1% (95%CI 9.9-14.5%) of those with type 2 diabetes. The risk of elevated ALT in patients with type 2 diabetes increased with increasing body mass index (p(trend) = 0.04), and was lower in those taking insulin (OR 0.38, 95%CI 0.22-0.65). DISCUSSION: The prevalence of elevated ALT is 3-4 times higher in patients with either type 1 or type 2 diabetes than in the general population. Further studies investigating the aetiology and mechanisms of this elevation may suggest appropriate early interventions.

Adolescent↗
PubMed2004

Correlation of serum aminotransferases with HCV RNA levels and histological findings in patients with chronic hepatitis C: the role of serum aspartate transaminase in the evaluation of disease progression.

OBJECTIVES: To investigate whether HCV RNA levels can be considered to be predictors of hepatocellular injury in patients with chronic hepatitis C, and whether aminotransferase levels are markers of liver damage. METHODS: We performed a retrospective study on 112 patients with chronic hepatitis C. For each patient, we considered the baseline alanine aminotransferase (ALT) and serum aspartate transaminase (AST) levels, baseline HCV RNA, HCV genotype, histological evaluation and the mean aminotransferase levels measured in the 6 months following liver biopsy. RESULTS: We found a statistically significant correlation between HCV RNA and aminotransferase levels measured during the follow-up (AST: r = 0.24, P = 0.01; ALT: r = 0.27, P = 0.004). We also observed a statistically significant correlation between HCV RNA levels and histological activity index (HAI) (r = 0.25, P = 0.008), as well as between the HAI and both baseline AST (r = 0.34, P = 0.0002) and ALT levels (r = 0.23, P = 0.01). These findings were confirmed by the mean aminotransferase values during follow-up. In the regression analysis, the fibrosis score was significantly and independently associated with baseline AST and ALT values. CONCLUSIONS: Our results demonstrate a statistically significant correlation of aminotransferase values with the histological parameters, and an even stronger correlation with the AST values. Our study therefore suggests that aminotransferase values, especially AST, may correlate with liver damage.

Adult↗
PubMed2004

Associations between serum leptin levels and transaminase activities and the status of lifestyle in Japanese workers.

BACKGROUND: Leptin has been implicated in the pathogenesis of various liver diseases. In this study, associations between serum leptin levels and serum transaminase activities and the statuses of various lifestyles, including that of ethanol consumption, were studied. METHODS: Associations between these factors were statistically examined in 122 Japanese men on the basis of the data taken from their health checkups. Individuals with cirrhosis, hepatitis virus infection, and autoimmune liver diseases were excluded. RESULTS: Spearman's simple regression analyses demonstrated that serum leptin levels correlated with serum activities of aspartate aminotransferase (r = 0.174, p = 0.0382) and alanine aminotransferase (ALT; r = 0.336, p < 0.0001) but not with serum gamma-glutamyl transpeptidase activity (r = 0.155, p = 0.0656). In multiple regression analysis in which subjects' age, levels of serum triglyceride, and insulin resistance index were adjusted, the logarithmic serum leptin level was significantly associated with logarithmic ALT activity (p = 0.004) but not with logarithmic aspartate aminotransferase activity (p = 0.134). ANOVA showed no significant association between serum leptin levels and total lifestyle status assessed by Breslow's index. Multiple logistic regression analysis showed that normal body mass index and proper exercise were factors accounting for maintaining a normal leptin level, whereas the ethanol consumption level did not affect the serum leptin level. No significant association between ethanol consumption and serum leptin level was confirmed by single regression analysis as well as by Spearman's simple regression test. CONCLUSION: Increased serum leptin is related to morbid conditions increasing ALT. Because the association between the degree of ethanol consumption and the serum leptin level was not significant, the reported association between the serum leptin level and alcoholic liver disease should, at least, not be a feature of its early stage.

Adult↗