scholarly journals Investigations of rat liver uroporphyrinogen decarboxylase. Comparisons of porphyrinogens I and III as substrates and the inhibition by porphyrins

1981 ◽  
Vol 195 (1) ◽  
pp. 241-250 ◽  
Author(s):  
A G Smith ◽  
J E Francis
Keyword(s):  
Rat Liver ◽  
Rapid Analysis ◽  
Oxidation Products ◽  
Decarboxylase Activity ◽  
Effective Inhibitor ◽  
Uroporphyrinogen Decarboxylase ◽  
The Difference ◽  
Substrate Concentrations ◽  
Slow Turnover

1. The decarboxylations of uroporphyrinogens, hepta-, hexa- and penta-carboxyporphyrinogens I and III by porphyrinogen carboxy-lyase (EC 4.1.1.37) in rat liver supernatant have been compared as functions of substrate concentrations. Although Km and Vmax. (for total porphyrinogens formed) were estimated, prophyrinogens and CO2 produced at 1 microM were considered to be a better indication of real relative rates, owing to substrate/product inhibitions. Uroporphyrinogen III was the best substrate by the criteria of Km/Vmax. and decarboxylation at 1 microM and was converted into coproporphyrinogen more quickly than its series-I isomer. 2. The difference between uroporphyrinogens I and III as substrates was confirmed by using a mixture of [14C8]uroporphyrinogens, the discrimination occurring principally in the first decarboxylation. 3. Porphyrins, especially oxidation products of the substrates, inhibited the enzyme. Heptacarboxyporphyrin III was the most effective inhibitor of both uroporphyrinogen III and heptacarboxyporphyrinogen III conversion into coproporphyrinogen. 4. Rapid analysis of the livers from rats made porphyric with hexachlorobenzene demonstrated that substantial quantities of the tetrapyrroles were present in vivo as the porphyrinogens (21-42%). 5. Enzymic decarboxylation of uroporphyrinogen III in 2H2O-containing buffer gave [2H4]coproporphyrinogen. 6. Rats treated with cycloheximide for 10h showed no decrease in uroporphyrinogen decarboxylase activity/mg of protein, suggesting a relatively slow turnover of the enzyme.

Autophagy of mitochondria in rat liver assessed by immunogold procedures.

1988 ◽  
Vol 36 (11) ◽  
pp. 1433-1440 ◽  
Author(s):  
E Knecht ◽  
A Martinez-Ramón ◽  
S Grisolia
Keyword(s):  
Glutamate Dehydrogenase ◽  
Rat Liver ◽  
Polyclonal Antibodies ◽  
Carbamoyl Phosphate ◽  
Autophagic Vacuoles ◽  
The Difference ◽  
In Vivo Administration ◽  
Phosphate Synthase

Glutamate dehydrogenase and carbamoyl phosphate synthase-I were localized in rat liver by immunogold procedures, using monoclonal and polyclonal antibodies. As expected, there was extensive labeling in mitochondria. Label was also found in lysosomal autophagic vacuoles. When autophagy was stimulated by in vivo administration of the anti-microtubular agent vinblastine we found that: (a) carbamoyl phosphate synthase-I and glutamate dehydrogenase could be found in mitochondria within autophagic vacuoles; (b) the carbamoyl phosphate synthase-I and glutamate dehydrogenase content of the mitochondria sequestered into autophagic vacuoles is the same as that of the nearby "free" mitochondria; and (c) in the whole liver, autophagic vacuoles contain c. 1.5 times more glutamate dehydrogenase than carbamoyl phosphate synthase-I, in contrast to mitochondria which have c. three times more carbamoyl phosphate synthase-I than glutamate dehydrogenase. The latter finding could explain, at least partially, the difference in half-lives of these enzymes.

Alcohol-Induced Decrease in Uroporphyrinogen Decarboxylase Activity in Rat Liver and Spleen

Enzyme ◽  
1981 ◽  
Vol 26 (1) ◽  
pp. 24-31 ◽  
Author(s):  
M. Doss ◽  
R. von Tiepermann ◽  
G. Stutz ◽  
R. Teschke
Keyword(s):  
Rat Liver ◽  
Decarboxylase Activity ◽  
Uroporphyrinogen Decarboxylase

Kinetics of Distribution of D2O and Antipyrine in Isolated Perfused Rat Liver

1958 ◽  
Vol 192 (3) ◽  
pp. 531-537 ◽  
Author(s):  
Alan M. Thompson ◽  
H. Mead Cavert ◽  
Nathan Lifson
Keyword(s):  
Rat Liver ◽  
Early Period ◽  
Tissue Perfusion ◽  
Isolated Perfused Rat Liver ◽  
Perfused Rat Liver ◽  
Rate Of Increase ◽  
The Difference ◽  
Rat Livers ◽  
Kinetics Of

Isolated rat livers were perfused via the portal vein with a blood-Ringer mixture containing a constant inflow concentration of D2O and, in some cases, antipyrine. The rate of increase of outflow concentration was studied, comparisons being made between D2O, antipyrine and a theoretical outflow curve based on completely flow-limited distribution. The effect of flow rate on the deviation of D2O from theoretical was also studied. The results indicate that exchange of D2O and antipyrine between blood and tissue in the perfused rat liver is extremely rapid relative to the rate of blood supply of these substances to the organ, even at flows several times that occurring in vivo. In the average experiment the average D2O concentration in the liver during the early period of the perfusion was about 90% of the mixed venous concentration. The factors responsible for the failure of D2O to distribute maximally, particularly tissue perfusion heterogeneity and diffusion limitation, are discussed. Although quantitation of the difference is difficult, antipyrine appears to distribute somewhat more rapidly than D2O due to its greater solubility in cell membranes.

Uptake of plasma free fatty acids by the isolated rat liver: effect of glucagon

1963 ◽  
Vol 205 (4) ◽  
pp. 667-670 ◽  
Author(s):  
Abdullah Aydin ◽  
Joseph E. Sokal
Keyword(s):  
Fatty Acid ◽  
Rat Liver ◽  
Experimental System ◽  
Plasma Free Fatty Acid ◽  
Isolated Perfused Rat Liver ◽  
Isolated Rat Liver ◽  
Uptake Rates ◽  
The Difference ◽  
Isolated Rat

The uptake of oleate by the isolated perfused rat liver was studied over the range of plasma free fatty acid (FFA) concentration from 100 to 1,800 µEq/liter. Hepatic removal of FFA could be described as a linear function of the FFA concentration in blood entering the liver. When appropriate correction was made for the difference in metabolic rates of the two species, it was found that the isolated rat liver removed FFA from its perfusing blood at rates quite comparable to those reported for the dog liver in vivo. An effect of glucagon on FFA uptake rates could not be demonstrated, either with fasted or with glycogen-containing livers. This experimental system, which offers the advantages of relatively easy control of many variables and of exclusion of the effects of other organs, appears well suited for studies of fatty acid metabolism in the liver.

scholarly journals The effects in vivo of mutationally modified uroporphyrinogen decarboxylase in different hem12 mutants of baker's yeast (Saccharomyces cerevisiae)

1988 ◽  
Vol 253 (1) ◽  
pp. 109-116 ◽  
Author(s):  
A Kurlandzka ◽  
T Zoladek ◽  
J Rytka ◽  
R Labbe-Bois ◽  
D Urban-Grimal
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Porphyria Cutanea Tarda ◽  
Baker’S Yeast ◽  
Decarboxylase Activity ◽  
Baker's Yeast ◽  
Uroporphyrinogen Decarboxylase ◽  
Human Form ◽  
Yeast Saccharomyces Cerevisiae ◽  
Diploid Cells

Nine new hem12 haploid mutants of baker's yeast (Saccharomyces cerevisiae), totally or partially deficient in uroporphyrinogen decarboxylase activity, were subjected to both genetic and biochemical analysis. The mutations sites studied are situated far apart within the HEM12 gene located on chromosome IV. Uroporphyrinogen decarboxylase activity in the cell-free extracts of the mutants was decreased by 50-100%. This correlated well with the decrease of haem formation and the increased accumulation and excretion of porphyrins observed in vivo. The pattern of porphyrins (uroporphyrin and its decarboxylation products) accumulated in the cells of mutants partially deficient in uroporphyrinogen decarboxylase activity did not differ significantly, although differences in vitro were found in the relative activity of the mutant enzyme at the four decarboxylation steps. The excreted porphyrins comprised mainly dehydroisocoproporphyrin or pentacarboxyporphyrin. In heterozygous hem12-1/HEM12 diploid cells, a 50% decrease in decarboxylase activity led to an increased accumulation of porphyrins as compared with the wild-type HEM12/HEM12 diploid, which points to the semi-dominant character of the hem12-1 mutation. The biochemical phenotypes of both the haploid and the heterozygous diploid resembles closely the situation encountered in porphyria cutanea tarda, the most common human form of porphyria.

The Effect of the Porphyrogenic Compound, Hexachlorobenzene, on the Activity of Hepatic Uroporphyrinogen Decarboxylase in the Rat

1976 ◽  
Vol 51 (1) ◽  
pp. 71-80 ◽  
Author(s):  
G. H. Elder ◽  
J. O. Evans ◽  
S. A. Matlin
Keyword(s):  
Rat Liver ◽  
Wistar Rats ◽  
New Method ◽  
Decarboxylase Activity ◽  
Uroporphyrinogen Decarboxylase ◽  
Enzyme Defect ◽  
Female Wistar Rats ◽  
Liver Homogenates

1. A new method for the measurement of uroporphyrinogen decarboxylase (EC 4.1.1.37) in rat liver homogenates, with 5-carboxyl porphyrinogen as substrate, is described. 2. The administration of a diet containing 0·3% (w/w) hexachlorobenzene produces porphyria in female Wistar rats after a delay of at least 4 weeks. The development of porphyria is accompanied by a progressive fall in hepatic uroporphyrinogen decarboxylase activity to 18% of control values after 11 weeks. The features of hexachlorobenzene porphyria are consequences of this enzyme defect. 3. Feeding with hexachlorobenzene did not lead to the accumulation of iron in the liver. It is suggested that hexachlorobenzene or a metabolite acts directly to decrease the activity of the enzyme.

Sign in / Sign up

Export Citation Format

Share Document