scholarly journals Rat liver contains a potent endogenous inhibitor of inositol 1,3,4,5-tetrakisphosphate 3-phosphatase

1990 ◽  
Vol 267 (3) ◽  
pp. 831-834 ◽  
Author(s):  
M E Hodgson ◽  
S B Shears
Keyword(s):  
Ion Exchange ◽  
Phosphatase Activity ◽  
Rat Liver ◽  
Ion Exchange Chromatography ◽  
Exchange Chromatography ◽  
Endogenous Inhibitor ◽  
Stable Factor ◽  
Heat Stable

When Ins(1,3,4,5)P4 was incubated with a rat liver 100,000 g supernatant, about 93% of the substrate was metabolized by a 5-phosphatase, and only 7% by a 3-phosphatase. Ion-exchange chromatography of the supernatant specifically increased its 3-phosphatase activity 72 +/- 3-fold. This activated enzyme was inhibited by a heat-stable factor present in both the soluble and particulate portions of the cell.

scholarly journals Regulation of the pentose phosphate cycle Cofactor that controls the inhibition of glucose-6-phosphate dehydrogenase by NADPH in rat liver

1986 ◽  
Vol 239 (3) ◽  
pp. 553-558 ◽  
Author(s):  
M Nogueira ◽  
G Garcia ◽  
C Mejuto ◽  
M Freire
Keyword(s):  
Ion Exchange ◽  
Rat Liver ◽  
Pentose Phosphate Pathway ◽  
Reductase Activity ◽  
Gel Filtration ◽  
Ion Exchange Chromatography ◽  
Exchange Chromatography ◽  
Pentose Phosphate ◽  
Glutathione Reductase Activity ◽  
Glucose 6 Phosphate Dehydrogenase

A cofactor of Mr 10(4), characterized as a polypeptide, was found to co-operate with GSSG to prevent the inhibition of glucose-6-phosphate dehydrogenase by NADPH, in order to ensure the operation of the oxidative phase of the pentose phosphate pathway, in rat liver [Eggleston & Krebs (1974) Biochem. J. 138, 425-435; Rodriguez-Segade, Carrion & Freire (1979) Biochem. Biophys. Res. Commun. 89, 148-154]. This cofactor has now been partially purified by ion-exchange chromatography and molecular gel filtration, and characterized as a protein of Mr 10(5). The lighter cofactor reported previously was apparently the result of proteolytic activity generated during the tissue homogenization. The heavier cofactor was unstable, and its amount increased in livers of rats fed on carbohydrate-rich diet. Since the purified cofactor contained no glutathione reductase activity, the involvement of this enzyme in the deinhibitory mechanism of glucose-6-phosphate dehydrogenase by NADPH should be ruled out.

scholarly journals Heat-stable enterotoxins from Escherichia coli P16

1980 ◽  
Vol 28 (3) ◽  
pp. 1038-1040
Author(s):  
M N Burgess ◽  
N A Mullan ◽  
P M Newsome
Keyword(s):  
Escherichia Coli ◽  
Ion Exchange ◽  
Isoelectric Focusing ◽  
Ion Exchange Chromatography ◽  
Exchange Chromatography ◽  
Infant Mouse ◽  
Heat Stable

Escherichia coli P16 infant mouse active heat-stable enterotoxin may be fractionated into two distinct active moieties by ion-exchange chromatography, Sephadex G-25 chromatography, and isoelectric focusing.

scholarly journals Biosynthesis of serum albumin in rat liver. Evidence for the existence of ‘proalbumin’

1973 ◽  
Vol 134 (4) ◽  
pp. 1083-1091 ◽  
Author(s):  
J. D. Judah ◽  
Margaret Gamble ◽  
J. H. Steadman
Keyword(s):  
Ion Exchange ◽  
Rat Liver ◽  
Microsomal Fraction ◽  
Peptide Mapping ◽  
Protein S ◽  
Ion Exchange Chromatography ◽  
Exchange Chromatography ◽  
Small Peptide ◽  
Previous Suggestion ◽  
Tryptic Hydrolysis

1. A protein(s) of rat liver (precipitated from soluble extracts of the microsomal fraction by anti-albumin) yields albumin after limited hydrolysis by trypsin. 2. Evidence that the product of limited tryptic hydrolysis is albumin, is based upon ion-exchange chromatography, electrofocusing and peptide `mapping'. 3. The albumin `precursor' is recognized by anti-albumin and is apparently not distinguished from albumin by anti-albumin. 4. A small peptide is liberated from the presumptive albumin precursor during limited tryptic hydrolysis. This peptide is labelled by arginine, but not by leucine, lysine or methionine. 5. These results support our previous suggestion based on kinetic evidence that the albumin-like protein(s), in the anti-albumin precipitate from rat liver, is an albumin precursor.

scholarly journals Evidence for a protein regulator from rat liver which activates acetyl-CoA carboxylase

1993 ◽  
Vol 292 (1) ◽  
pp. 75-84 ◽  
Author(s):  
K A Quayle ◽  
R M Denton ◽  
R W Brownsey
Keyword(s):  
Ion Exchange ◽  
Rat Liver ◽  
High Speed ◽  
Deae Cellulose ◽  
Ion Exchange Chromatography ◽  
Exchange Chromatography ◽  
Size Exclusion ◽  
Acetyl Coa Carboxylase ◽  
Acetyl Coa ◽  
Carboxylase Activity

1. A regulator of acetyl-CoA carboxylase has been identified in high-speed supernatant fractions from rat liver. The regulator was found to activate highly purified acetyl-CoA carboxylase 2-3-fold at physiological citrate concentrations (0.1-0.5 mM). The effects of the regulator on acetyl-CoA carboxylase activity were dose-dependent, and half-maximal activation occurred in 7-8 min at 30 degrees C. 2. The acetyl-CoA carboxylase regulator was non-dialysable and was inactivated by heating or by exposure to carboxypeptidase. The regulator was enriched from rat liver cytosol by first removing the endogenous acetyl-CoA carboxylase and then using a combination of purification steps, including (NH4)2SO4 precipitation, ion-exchange chromatography and size-exclusion chromatography. The regulator activity appeared to be a protein with a molecular mass of approx. 75 kDa, which could be eluted from mono-Q with approx. 0.35 M KCl as a single peak of activity. 3. Studies of the effects of the regulator on phosphorylation or subunit size of acetyl-CoA carboxylase indicated that the changes in enzyme activity are most unlikely to be explained by dephosphorylation or by proteolytic cleavage. 4. The regulator co-migrates with acetyl-CoA carboxylase through several purification steps, including ion-exchange chromatography and precipitation with (NH4)2SO4; however, the proteins may be separated by Sepharose-avidin chromatography, and the association between the proteins is also disrupted by addition of avidin in solution. Furthermore, the binding of the regulator itself to DEAE-cellulose is altered by the presence of acetyl-CoA carboxylase. Taken together, these observations suggest that the effects of the regulator on acetyl-CoA carboxylase may be explained by direct protein-protein interaction in vitro.

scholarly journals Microsomal epoxide hydrolase of rat liver. Purification and characterization of enzyme fractions with different chromatographic characteristics

1986 ◽  
Vol 233 (2) ◽  
pp. 607-611 ◽  
Author(s):  
N J Bulleid ◽  
A B Graham ◽  
J A Craft
Keyword(s):  
Ion Exchange ◽  
Rat Liver ◽  
Epoxide Hydrolase ◽  
Ion Exchange Chromatography ◽  
Exchange Chromatography ◽  
Phospholipid Content ◽  
Microsomal Epoxide Hydrolase ◽  
Ionic Detergent ◽  
Inhibited Enzyme

Microsomal epoxide hydrolase was purified from rat liver, and different fractions of the purified enzyme, which varied in their contents of phospholipid, were obtained by ion-exchange chromatography. One fraction (A), which did not bind to CM-cellulose, had a high phospholipid content, and a second fraction (B), which was eluted from CM-cellulose at high ionic strength, had a low phospholipid content. Removal of most of the phospholipid from fraction A altered its chromatographic behaviour. When the delipidated material was re-applied to CM-cellulose, most of the enzyme bound to the cation-exchanger. The specific activities of all the fractions described (with styrene epoxide [(1,2-epoxyethyl)benzene] as substrate) were altered by adding the non-ionic detergent Lubrol PX or phospholipid. Lubrol PX inhibited enzyme activity, and phospholipid reversed this inhibition. The various enzyme fractions isolated appeared to be different forms of the same protein, as judged by their minimum Mr values and immunochemical properties. These results indicate that different fractions of epoxide hydrolase isolated by ion-exchange chromatography probably are not different isoenzyme forms.

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