[14] Glycogen synthetase from rat liver

Arulselvan

JOURNAL OF HEALTH SCIENCE

et al. 2006

176

The present study was aimed to evaluate the anti-diabetic potential of Terminalia chebula (T. chebula) fruits on streptozotocin (STZ)-induced experimental diabetes in rats. Oral administration of ethanolic extract of the fruits (200 mg/kg body weight/rat/day) for 30 days significantly reduced the levels of blood glucose and glycosylated hemoglobin in diabetic rats. Determination of plasma insulin levels revealed the insulin stimulating action of the fruit extract. Also, the alterations observed in the activities of carbohydrate and glycogen metabolising enzymes were reverted back to near normal after 30 days of treatment with the extract. Electron microscopic studies showed significant morphological changes in the mitochondria and endoplasmic reticulum of pancreatic β cells of STZinduced diabetic rats. Also, a decrease in the number of secretory granules of β-cells was observed in the STZinduced diabetic rats and a these pathological abnormalities were normalized after treatment with T. chebula extract. The efficacy of the fruit extract was comparable with glibenclamide, a well known hypoglycemic drug.

Section: )mentioning

confidence: 99%

Anti-Diabetic Activity of Fruits of Terminalia chebula on Streptozotocin Induced Diabetic Rats

Arulselvan

JOURNAL OF HEALTH SCIENCE

et al. 2006

176

European Journal of Biochemistry

“…Leloir et al [46] have observed that when a liver homogenate is fractionated by differential centrifugation most of glycogen synthase and phosphorylase is recovered with the glycogen.…”

Section: Is Marked By Arrow (Bj the Sume Cell ~~I T H Imnztrnoreactimentioning

confidence: 99%

Isolation of the low‐molecular‐mass form of catechol O‐methyltransferase from rat liver and immunocytochemical localization of the enzyme in the glycogen compartment

Veser

Martin

1986

The low-molecular-mass form of two distinct catechol 0-methyltransferase activities (S-adenosyl-Lmethionine : catechol 0-methyltransferase, COMT, EC 2.1.1.6) has been purified to homogeneity from rat liver using 40 -70% ammonium sulfate precipitation, gel filtration on Sephadex G-100, adsorption on hydroxyapatite C and ion-exchange chromatography on DEAE-Sepharose CL-6B. The relative molecular mass M,, determined by sodium dodecyl sulfate/polyacrylamide gel electrophoresis is 22400 f 500. Irradiation of the enzyme in the presence of 8-a~ido-[methyl-~HIAdoMet results in the specific labeling of the catalytic site of the enzyme. Photolabeling was successful with crude COMT preparations and with the isolated enzyme. Immunocytocheniical studies present new information about the localization of the low-molecular-mass form in the liver parenchyma. Subcellularly C O W immunoreactivity could be attributed exclusively to the compartment with glycogen granules. Nucleus, mitochondria and endoplasmic reticulum showed no immunostaining.The transfer of the methyl group from AdoMet to a variety of methyl acceptors such as catechol compounds [l, 21, phospholipids [3, 41, nucleic acids 151, neuropeptides and proteins [6] is catalysed by methyltransferases. Moreover, these enzymes have a regulatory function in the modulation of the concentration of AdoMet. The catecholic compounds are methylated by the enzyme S-adenosyl-L-methionine: catechol 0-methyltransferase (COMT). Numerous investigations have demonstrated COMT in a variety of animal tissues and cells, with the highest levels present in liver and kidney [7]. Metabolic studies have clearly shown that the primary site of 0-methylation of circulating catecholamines is the liver. The fact that COMT is found in high quantity in the 100000 x g supernatant of liver extracts does not indicate the precise location within the cell, whether it is free in the cytoplasm or loosely bound to membranes and released during homogenization. In 1974 [S] a form of COMT which is firmly bound to membranes was solubilized and partially purified from liver microsomes of the rat, but the microsomal COMT represented only about 0.1% of the total activity and was not released in the presence of saturated sodium chloride. The membraneassociated form exhibited biochemical and immunological properties similar to those of the soluble COMT.Correspondence to J. Veser, Abteilung Physiologische Chemie, Abbreviations. AdoMet, S-adenosyl-L-methionine; COMT, catEnzyme. S-Adenosyl-L-methionine : catechol 0-methyltransferase

European Journal of Biochemistry

“…After this preincubation period, I00 pl of the complete incubation mixture were added, and pyruvate kinase activity was tested according to the hydrazone method [19]. Protein was stained with 0.2O/, Coomassie brilliant blue in 7.5O/, acetic acid, after fixing the gels in 12.5O/, trichloroacetic acid for 30 min.…”

Section: Polyacrylamide Gel Electrophoresismentioning

confidence: 99%

Two types of Pyruvate Kinase in Mucor rouxii

Terenzi¹,

Roselino²,

Passeron³

1971

Extracts of mycelium of Mucor rouxii have been shown to contain two forms of pyruvate kinase named Type I and 11. They can be separated by DEAE-cellulose chromatography and by electrophoresis in polyacrylamide gel.Extracts from ungerminated sporangiospores or yeast-like cells contained only the Type I form. Pyruvate kinase Type I1 appears during aerobic germination of spores or during conversion of yeast-like cells to mycelium.Both pyruvate kinases are similar in their molecular weight, pH range of activity, K , with respect to substrates and their response to activators (Mn++ and fructose 1,6-diphosphate).illucor rouxii, a phycomycete fungus, displays a striking phenomenon of morphogenetic adaptation in accordance with the growth environment. I n anaerobiosis or under any condition which favours a high level of fermentation sporangiospores germinate producing yeast-like cells which reproduce by budding [l]. On the other hand, aerobic development leads to the formation of a typical mycelium. Therefore, it seems likely that the enzymes of the glycolytic pathway might participate in the control of morphological change.I n order to gain insight into the process of morphogenesis, a general study of one of the key glycolytic enzymes, pyruvate kinase, was undertaken.It is already known that the cellular activity of pyruvate kinase seems to be subject to several types of control. Pyruvate kinase from many sources [X -81 is an allosteric protein, the enzymatic activity being controlled by the substrate (phosphoenol pyruvate) and the activator (fructose 1,6-diphosphate).The hormonal and nutritional state of organisms affects also the amount of pyruvate kinase [9-131; the pyruvate kinase content of the tissues is lower during gluconeogenesis than under conditions requiring carbohydrate breakdown.It has also been shown that rat liver [ l l ] and Escherichia coli K12 [14] contain two forms of the enzyme; one of these is activated by Fru-l,6-P2 and is inducible, the other is not affected by Fru-1,6-P2 and appears to be formed constitutively.I n a previous communication and that in addition to Fru-I,6-P2, Mn++ also acts as an allosteric activator a t low concentration of substrate (P-pyruvate).I n this paper we present evidences that the mycelium of 2M. rouxii has two forms of pyruvate kinase, tentatively named Type I and 11. Both activities could be separated by DEAE-cellulose chromatography and by electrophoresis in polyacrylamide gel.Pyruvate CulturesSpores of M . rouxii were produced and stored as described by Haidle and Storck [IS]. A complex medium (YPG) was used to grow the organism [17].The spore inoculum was about 5 x lo5 spores/ml of medium.