Identity of alanine:glyoxylate aminotransferase with alanine:2-oxoglutarate aminotransferase in rat liver cytosol

Rat liver soluble fraction contained 3 forms of alanine: glyoxylate aminotransferase. One with a pI of 5.2 and an Mr of approx. 110,000 was found to be identical with cytosolic alanine:2-oxoglutarate aminotransferase. The pI 6.0 enzyme with an Mr of approx. 220,000 was suggested to be from broken mitochondrial alanine:glyoxylate aminotransferase 2 and the pI 8.0 enzyme with an Mr of approx. 80,000 enzyme from broken peroxisomal and mitochondrial alanine:glyoxylate aminotransferase 1. These results suggest that the cytosolic alanine: glyoxylate aminotransferase activity is due to cytosolic alanine: 2-oxoglutarate aminotransferase.     

Intramitochondrial localization of alanine aminotransferase in rat-liver mitochondria: comparison with glutaminase and aspartate aminotransferase

Summary The removal of the outer mitochondrial membrane and hence of constituents of the intermembrane space in rat-liver mitochondria using digitonin showed that phosphate-dependent glutaminase, alanine and aspartate aminotransferase were localized in the mitoplasts. Further fractionation of mitoplasts following their sonication resulted in 90% of glutaminase, 98% of alanine aminotransferase and 48% of aspartate aminotransferase being recovered in the soluble fraction while the remainder of each enzyme was recovered in the sonicated vesicles fraction. These results indicated that glutaminase and alanine aminotransferase were soluble matrix enzymes, the little of each enzyme recovered in the sonicated vesicles fraction being probably due to entrapment in the vesicles. Aspartate aminotransferase had dual localization, in the inner membrane and matrix with the high specific activity in sonicated vesicles confirming its association with the membrane. Activation experiments suggested that the membrane-bound enzyme was localized on the inner side of the inner mitochondrial membrane.     

Studies on alanine aminotransferase in nematodes

L-alanine aminotransferase was demonstrated in a range of gastrointestinal, free-living and entomophagous nematodes. As in mammals, nematode L-alanine aminotransferase was found to exist in the form of mitochondrial and cytosolic isoenzymes. Whilst the majority of nematode enzymes exhibited a greater overall capacity for L-alanine synthesis than for L-alanine catabolism in vitro, the opposite was true for rat liver L-alanine aminotransferase. In contrast with rat liver, certain gastrointestinal nematodes were apparently able to transaminate D-alanine at low rates. H. contortus cytosolic L-alanine aminotransferase differed significantly from the mammalian enzyme with respect to both thermal stability and response to potential protective reagents.     

Immunocytochemical localization of human hepatic alanine: glyoxylate aminotransferase in control subjects and patients with primary hyperoxaluria type 1

Primary hyperoxaluria type 1 (PH1) is an inherited disorder of glyoxylate metabolism caused by a deficiency of the hepatic peroxisomal enzyme alanine: glyoxylate aminotransferase (AGT; EC 2.6.1.44) [FEBS Lett (1986) 201:20]. The aim of the present study was to investigate the intracellular distribution of immunoreactive AGT protein, using protein A-gold immunocytochemistry, in normal human liver and in livers of PH1 patients with (CRM+) or without (CRM-) immunologically crossreacting enzyme protein. In all CRM+ individuals, which included three controls, a PH1 heterozygote and a PH1 homozygote immunoreactive AGT protein was confined to peroxisomes, where it was randomly dispersed throughout the peroxisomal matrix with no obvious association with the peroxisomal membrane. No AGT protein could be detected in the peroxisomes or other cytoplasmic compartments in the livers of CRM- PH1 patients (homozygotes). The peroxisomal labeling density in the CRM+ PH1 patient, who was completely deficient in AGT enzyme activity, was similar to that of the controls. In addition, in the PH1 heterozygote, who had one third normal AGT enzyme activity, peroxisomal labeling density was reduced to 50% of normal.     

Substantial changes in epicardial fat thickness after weight loss in severely obese subjects

We sought to evaluate the effect of weight loss on echocardiographic epicardial fat thickness, as index of visceral adiposity, and whether epicardial fat change after the weight loss can be proportionally different from overall body weight changes and related to cardiac parameters changes in severely obese subjects. This was an interventional study in 20 severely obese subjects (12 women, 8 men, BMI 45+/-5 kg/m(2), 35+/-10 years) who underwent 6-month very low calorie diet weight loss program. Baseline and after 6-month weight loss anthropometrics, echocardiographic epicardial fat thickness, left ventricular mass (LVM), and diastolic function parameters were assessed. Subjects lost 20% of original body weight, BMI reduced by 19% of original BMI, waist circumference decreased by 23% of initial waist circumference. Epicardial fat thickness decreased from 12.3+/-1.8 to 8.3+/-1 mm P<0.001 after the 6-month very low calorie diet, as -32% of baseline epicardial fat thickness. LVM and diastolic function changes were better correlated with epicardial fat changes. We showed that significant weight loss can be associated with significant reduction in the epicardial fat thickness, marker of visceral adiposity in severely obese subjects. Epicardial fat decrease, therefore visceral fat decrease, can be proportionally higher than overall adiposity decrease. Epicardial fat changes are significantly associated with obesity-related cardiac morphological and functional changes during weight loss. Measurement of echocardiographic epicardial fat thickness may provide an additional tool in understanding the metabolic risk associated with variation in fat distribution.     

家蚕丙氨酸转氨酶的纯化与鉴定

应用细胞匀浆,硫酸铵分段盐析,DEAE-纤维素柱层析和羟基磷灰石柱层析等方法,从家蚕后部丝腺中成功地分离制备了高纯度的丙氨酸转氨酶,经聚丙烯酰胺凝胶电泳分析鉴定,本法制备的丙氨酸转氨酶已达到均一的纯度。     

A recombinant tyrosine aminotransferase from Trypanosoma cruzi has both tyrosine aminotransferase and alanine aminotransferase activities

Abstract Tyrosine aminotransferase purified from epimastigotes of Trypanosoma cruzi displays an additional activity of alanine aminotransferase, absent in all other tyrosine aminotransferases characterized so far. Since the parasite's genome contains a high number of copies of the tyrosine aminotransferase gene, we could not rule out the possibility that two very similar proteins, with changed specificity due to a few amino acid substitutions, might be responsible for the two activities. We have now expressed in Escherichia coli a recombinant tyrosine aminotransferase as a fusion protein with glutathione S-trans-ferase. The purified fusion protein, intact or after thrombin cleavage, displays tyrosine aminotransferase and alanine aminotransferase activities with apparent K m values similar to those for the natural enzyme, thus proving that they belong to the same protein.     

Distribution pattern of alanine aminotransferase activity in rat liver

Summary Activities of the alanine aminotransferase were measured along the entire sinusoidal paths (1) between small portal tracts and central veins and (2) between regions of adjoining septal branches and central veins in the livers of male Wistar rats using a Lowry technique. The established profiles of enzyme activity give support to previous studies, suggesting functional heterogeneity of liver sinusoids and their abutting hepatocytes related to morphological differences of the sinusoidal bed.Dedicated to Professor Dr. T.H. Schiebler on occasion of his 65th birthdaySupported by grants of the Forschungsförderung des Landes Nordrhein-Westfalen, No. 40002585 and the Verein der Förderer und Freunded der Universität Köln     

Anaerobic induction of alanine aminotransferase in barley root tissue

Alanine aminotransferase, otherwise called glutamate-pyruvate aminotransferase (GPT), activity increases up to fourfold during several days of anaerobic induction in barley (Hordeum vulgare L.) roots, reaching a maximum activity of 13 international units per gram fresh weight. This increase in activity paralleled the increase in alcohol dehydrogenase activity in the same root tissue. Upon return to aerobic conditions, the induced GPT activity declined with an apparent half-life of 2 days. The isozyme profile of GPT in barley root tissue comprised one band of activity; in maize there were three bands of activity, the bands with greater mobility had much lower activity. Native polyacrylamide gel electrophoresis indicated that the induction of GPT activity results from an increase in the level of activity of these bands; no other activities were detected. When root tissue was induced under different levels of hypoxia (0%, 2%, 5%, and 21% O₂), changes in GPT activity were found to increase with lower levels of oxygen. Comparisons of GPT induction in barley, maize (Zea mays), rye, (Secale cereale) and wheat (Triticum aestivum) indicate that this enzyme is induced in the root tissue of all of these cereals; however, anaerobic root conditions do not result in the induction of GPT activity in leaf tissue. The dependence of GPT induction on high levels of nitrate in the media was tested by comparing activity levels in Hoagland solution and a nitrate-free nutrient solution. GPT activity was induced to similar levels under both conditions. These results indicate that alanine aminotransferase shows a very similar pattern of induction to alcohol dehydrogenase in barley root tissue and may be important in anaerobic glycolysis.     

Distribution pattern of alanine aminotransferase activity in rat liver

Activities of the alanine aminotransferase were measured along the entire sinusoidal paths (1) between small portal tracts and central veins and (2) between regions of adjoining septal branches and central veins in the livers of male Wistar rats using a Lowry technique. The established profiles of enzyme activity give support to previous studies, suggesting functional heterogeneity of liver sinusoids and their abutting hepatocytes related to morphological differences of the sinusoidal bed.     

Stabilization of alanine aminotransferase by consecutive modification and immobilization

Summary A new combination of methodologies for enzyme stabilization has been carried out. Dimethylsuberimidate-modified alanine aminotransferase was covalently immobilized on a preactivated agarose gel. The resulting derivative showed greater residual activity than the immobilized-only counterpart, maintaining the same amount of immobilized enzyme and its stability was greater than the native, modified and immobilized enzymes in several conditions.     

Activity, location, and role of asparate aminotransferase and alanine aminotransferase isoenzymes in leaves with C4 pathway photosynthesis

Further evidence has been provided that C₄-pathway species characterized by having low malic enzyme activity contain exceptionally high activities of aspartate and alanine aminotransferases. The total activity of both enzymes is distributed about equally between mesophyll and bundle sheath cells. However, the activity in the two cell types is due to different isoenzymes. In addition to the one quantitatively major isoenzyme associated with each cell type there were at least two additional isozymes of each aminotransferase detectable in the different species examined. Increases in activity of both aminotransferases of ten-fold or more were observed during greening of leaves of dark-grown plants. This increased activity was due specifically to the two quantitatively major isoenzymes associated, respectively, with the mesophyll and bundle sheath cells of green leaves, providing further evidence for their specific role in photosynthesis. Apparently, neither the aspartate nor alanine aminotransferases of mesophyll cells was associated with chloroplasts or other subcellular organelles. However, the major aspartate aminotransferase isoenzyme of bundle sheath cells was associated with mitochondria. These findings are discussed in relation to the probable role of aspartate and alanine aminotransferases in C₄-pathway photosynthesis.