Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P01275 (glucagon)
 26,492 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

After glucagon injection, rats showed virtually identical percentage increases in hepatic histidine-pyruvate aminotransferase and serine-pyruvate aminotransferase activities, both in the mitochondria and in the cytosol. Histidine-pyruvate aminotransferase isoenzyme 1, with pI8.0, was purified to homogeneity from the mitochondrial fraction of liver from glucagon-injected rats. The purified enzyme catalysed transamination between a number of amino acids and pyruvate or phenylpyruvate. For transamination with pyruvate, the activity with serine reached a constant ratio to that with histidine during purification, which was unchanged by a variety of treatments of the purified enzyme. Serine was found to act as a competitive inhibitor of histidine transamination, and histidine of serine transamination. These results suggest that histidine-pyruvate amino-transferase isoenzymes 1 is identical with serine-pyruvate aminotransferase. The enzyme is probably composed of two identical subunits with mol. wt. approx. 38000. The absorbance maximum at 410 nm and the inhibition by carbonyl reagents strongly indicate the presence of pyridoxal phosphate.
 ...
PMID:Identity of isoenzyme 1 of histidine-pyruvate aminotransferase with serine-pyruvate aminotransferase. 1 42

1. Histidine-pyruvate aminotransferase (isoenzyme 1) was purified to homogeneity from the mitochondrial and supernatant fractions of rat liver, as judged by polyacrylamide-gel electrophoresis and isolectric focusing. Both enzyme preparations were remarkably similar in physical and enzymic properties. Isoenzyme 1 had pI8.0 and a pH optimum of 9.0. The enzyme was active with pyruvate as amino acceptor but not with 2-oxoglutarate, and utilized various aromatic amino acids as amino donors in the following order of activity: phenylalanine greater than tyrosine greater than histidine. Very little activity was found with tryptophan and 5-hydroxytryptophan. The apparent Km values were about 2.6mM for histidine and 2.7 mM for phenylalanine. Km values for pyruvate were about 5.2mM with phenylalanine as amino donor and 1.1mM with histidine. The aminotransferase activity of the enzyme towards phenylalanine was inhibited by the addition of histidine. The mol.wt. determined by gel filtration and sucrose-density-gradient centrifugation was approx. 70000. The mitochondrial and supernatant isoenzyme 1 activities increased approximately 25-fold and 3.2-fold respectively in rats repeatedly injected with glucagon for 2 days. 2. An additional histidine-pyruvate aminotransferase (isoenzyme 2) was partially purified from both the mitochondrial and supernatant fractions of rat liver. Nearly identical properties were observed with both preparations. Isoenzyme 2 had pI5.2 and a pH optimum of 9.3. The enzyme was specific for pyruvate and did not function with 2-oxoglutarate. The order of effectiveness of amino donors was tyrosine = phenylalanine greater than histidine greater than tryptophan greater than 5-hydroxytryptophan. The apparent Km values for histidine and phenylalanine were about 0.51 and 1.8 mM respectively. Km values for pyruvate were about 3.5mM with phenylalanine and 4.7mM with histidine as amino donors. Histidine inhibited phenylalanine aminotransferase activity of the enzyme. Gel filtration and sucrose-density-gradient centrifugation yielded a mol.wt. of approx. 90000. Neither the mitochondrial nor the supernatant isoenzyme 2 activity was elevated by glucagon injection.
 ...
PMID:Purification, characterization and identification of rat liver histidine-pyruvate aminotransferase isoenzymes. 93 69

Thyrotropin-releasing hormone immunoreactivity (TRH-IR) was measured in isolated islets and in medium from rat pancreatic islets maintained in organ culture. TRH-IR in methanol extracts of both islets and culture medium was eluted in the same position as synthetic TRH by ion-exchange and gel chromatography and exhibited dilution curves parallel with synthetic TRH in radioimmunoassay. [3H]Histidine was incorporated into a component that reacted with TRH antiserum and had the same retention time as synthetic TRH on reversed-phase high-performance liquid chromatography. A continuous release of TRH-IR into the culture medium was observed from islets of both 5-d-old (newborn) and 30-d-old (adult) rats with a maximum on the second day of culture (28.7 +/- 7.0 and 13.3 +/- 3.6 fmol/islet per d, respectively). The content of TRH-IR was higher in freshly isolated islets from newborn rats (22.4 +/- 2.3 fmol/islet) than in adult rat islets, which, however, increased their content from 1.3 +/- 0.5 to 7.0 +/- 0.5 fmol/islet during the first 3 d of culture. Adult rat islets maintained in medium with 20 mM glucose released significantly more TRH-IR than islets in 3.3 mM glucose medium (13.0 +/- 0.7 vs. 4.3 +/- 0.3 fmol/islet per d). In contrast, the content of TRH-IR in the islets was reversed (1.4 +/- 0.3 vs. 4.7 +/- 1.6 fmol/islet). By exposing islets from newborn rats to streptozotocin 0.7 mg/ml for 30 min, a 50% reduction of TRH-IR content in the islets compared with the non-treated islets was seen after subsequent culture for 7 d. The insulin content was reduced by 80%, while glucagon was slightly elevated. In conclusion, these results indicate that TRH is synthesized in rat pancreatic islets, and that the release is stimulated by glucose.
 ...
PMID:Biosynthesis and release of thyrotropin-releasing hormone immunoreactivity in rat pancreatic islets in organ culture. Effects of age, glucose, and streptozotocin. 622 32

Glutamine transport was studied in preconfluent monolayered, mononucleated myoblasts (4 days old) and in fused, multinucleated, differentiated myotubes (10 days old), both prepared from neonatal rat skeletal muscle. The initial (60 s) rate of 50 microM glutamine uptake in myoblasts and myotubes was stereospecific, saturable, and largely (80%) Na+ dependent. At glutamine concentrations of 0.01-1 mM, Na(+)-dependent uptake showed saturation kinetics: in myoblasts, the Michaelis constant (Km) was 197 +/- 38 microM, maximum velocity (Vmax) was 1,165 +/- 60 pmol.min-1.mg protein-1; in myotubes, Km was 174 +/- 51 microM and Vmax was 1,435 +/- 47 pmol.min-1.mg protein-1. The Na(+)-dependent glutamine uptake was Li+ tolerant in both myoblasts and myotubes. The Na(+)-dependent uptake of 50 microM L-[3H]glutamine was investigated in the presence of various amino acids at 0.01-10 mM. Histidine and asparagine competitively inhibited glutamine uptake, but inhibition by serine was noncompetitive; glutamate, arginine, leucine, and 2-aminobicyclo(2,2,1)heptane-2-carboxylate (BCH) had no significant inhibitory effects; 2-(methyl-amino)isobutyrate (MeAIB) caused a small but significant inhibition. In parallel with a stimulation of glucose transport, addition of insulin stimulated Na(+)-dependent glutamine uptake within 1 h by a maximum of 27% in myoblasts and 42% in myotubes (half-maximal stimulation at 0.3 nM insulin). Glucagon had no effect. Kinetic analysis revealed that the insulin-stimulated increase in glutamine transport was due to a Vmax effect, which was cycloheximide inhibitable. The insulin-stimulated increase was Li+ tolerant and not inhibited by MeAIB or cysteine at 1 mM. The results indicate that the predominant glutamine transporter of neonatal rat skeletal muscle cells in primary tissue culture in System Nm. System Nm also appears to be the major insulin-sensitive glutamine transport component in skeletal muscle. Primary muscle culture appears to be a useful preparation for studying glutamine transport and its regulation.
 ...
PMID:Characteristics of glutamine transport in primary tissue culture of rat skeletal muscle. 833 46