scholarly journals A radiochemical method for the measurement of coproporphyrinogen oxidase and the utilization of substrates other than coproporphyrinogen III by the enzyme from rat liver

1978 ◽  
Vol 169 (1) ◽  
pp. 205-214 ◽  
Author(s):  
G H Elder ◽  
J O Evans
Keyword(s):  
Rat Liver ◽  
Protoporphyrin Ix ◽  
Competitive Inhibitor ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Sensitive Assay ◽  
Radiochemical Method ◽  
Mixed Substrate ◽  
Coproporphyrinogen Oxidase ◽  
Carboxyl Carbon

[14C2]Coproporphyrin III, 14C-labelled in the carboxyl carbon atoms of the 2- and 4-propionate substituents, was prepared by stepwise modification of the vinyl groups of protoporphyrin IX. The corresponding porphyrinogen was used as substrate in a specific sensitive assay for coproporphyrinogen oxidase (EC 1.3.3.3) in which the rate of production of 14CO2 is measured. With this method, the Km of the enzyme from rat liver for coproporphyrinogen III is 1.2 micron. Coproporphyrin III is a competitive inhibitor of the enzyme (Ki 7.6 micron). Apparent Km values for other substrates were measured by a mixed-substrate method: that for coproporphyrinogen IV is 0.9 micron and that for harderoporphyrinogen 1.6 micron. Rat liver mitochondria convert pentacarboxylate porphyrinogen III into dehydroisocoproporphyrinogen at a rate similar to that for the formation of protoporphyrinogen IX from coproporphyrinogen III. Mixed-substrate experiments indicate that this reaction is catalysed by coproporphyrinogen oxidase and that the Km for this substrate is 29 micron. It is suggested that the ratio of the concentration of pentacarboxylate porphyrinogen III to coproporphyrinogen III in the hepatocyte determines the relative rates of formation of dehydroisocoproporphyrinogen and protoporphyrinogen IX.

scholarly journals Uptake of protoporphyrin IX by isolated rat liver mitochondria

1980 ◽  
Vol 188 (2) ◽  
pp. 329-335 ◽  
Author(s):  
M E Koller ◽  
I Romslo
Keyword(s):  
Rat Liver ◽  
Mitochondrial Membrane ◽  
Protoporphyrin Ix ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Inner Mitochondrial Membrane ◽  
Erythropoietic Protoporphyria ◽  
Inner Membrane ◽  
Isolated Rat Liver ◽  
Isolated Rat

Rat liver mitochondria accumulate protoporphyrin IX from the suspending medium into the inner membrane in parallel with the magnitude of the transmembrane K+ gradient (K+in/K+out). Only protoporphyrin IX taken up in parallel with the transmembrane K+ gradient is available for haem synthesis. Coproporphyrins (isomers I and III) are not taken up by the mitochondria. The results support the suggestion by Elder & Evans [(1978) Biochem. J. 172, 345-347] that the prophyrin to be taken up by the inner mitochondrial membrane belongs to the protoporphyrin(ogen) IX series. Protoporphyrin IX at concentrations above 15 nmol/mg of protein has detrimental effects on the structural and functional integrity of the mitochondria. The relevance of these effects to the hepatic lesion in erythropoietic protoporphyria is discussed.

Transfer of Heme from Mitochondria in Rat Liver Cells

1972 ◽  
Vol 50 (6) ◽  
pp. 633-637 ◽  
Author(s):  
B. Yoda ◽  
L. G. Israels
Keyword(s):  
Rat Liver ◽  
Aminolevulinic Acid ◽  
Surrounding Medium ◽  
Protoporphyrin Ix ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Single Carrier ◽  
Protein Carriers ◽  
Rat Liver Cells

The final steps in heme synthesis take place within mitochondria while the acceptor apoproteins are synthesized on the endoplasmic reticulum. When 14C-δ-aminolevulinic acid is used as a heme precursor in intact rats, measurable 14C-heme is found to be associated with the microsomes within 10 min of intraperitoneal injection. This rapid transfer of heme from mitochondria was studied in vitro using isolated rat liver mitochondria, and protoporphyrin IX and 59Fe as heme precursors. These mitochondria synthesize heme when suspended in whole cell sap and this is only partially reduced by substituting Sephadex G-25 filtered cell sap or sucrose. Mitochondria incubated in G-25 filtered cell sap or sucrose synthesize equivalent amounts of heme but those in sucrose export little heme into the surrounding medium. Heme export from mitochondria is dependent on protein in the suspending medium. In cell sap, heme is associated with multiple proteins and no single carrier was identified. Heme probably makes its way from mitochondria to microsomes via various protein carriers by nonspecific adherence. Microsomal apoproteins or other heme binding proteins then remove the heme from the intermediate carrier as the terminal step.

Effects of 5-5'-Diphenyl-2-thiohydantoin (DPTH) and Thyroxine on the Ultrastructure and Chemical Composition of Rat Liver

1971 ◽  
Vol 29 ◽  
pp. 570-571
Author(s):  
E. A. Elfont ◽  
R. B. Tobin ◽  
D. G. Colton ◽  
M. A. Mehlman
Keyword(s):  
Chemical Composition ◽  
Rat Liver ◽  
Future Study ◽  
Mode Of Action ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Effective Inhibitor ◽  
Biochemical Effects ◽  
Glycerophosphate Dehydrogenase ◽  
Stimulation Of

Summary5,-5'-diphenyl-2-thiohydantoin (DPTH) is an effective inhibitor of thyroxine (T4) stimulation of α-glycerophosphate dehydrogenase in rat liver mitochondria. Because this finding indicated a possible tool for future study of the mode of action of thyroxine, the ultrastructural and biochemical effects of DPTH and/or thyroxine on rat liver mere investigated.Rats were fed either standard or DPTH (0.06%) diet for 30 days before T4 (250 ug/kg/day) was injected. Injection of T4 occurred daily for 10 days prior to sacrifice. After removal of the liver and kidneys, part of the tissue was frozen at -50°C for later biocheailcal analyses, while the rest was prefixed in buffered 3.5X glutaraldehyde (390 mOs) and post-fixed in buffered 1Z OsO4 (376 mOs). Tissues were embedded in Araldlte 502 and the sections examined in a Zeiss EM 9S.Hepatocytes from hyperthyroid rats (Fig. 2) demonstrated enlarged and more numerous mitochondria than those of controls (Fig. 1). Glycogen was almost totally absent from the cytoplasm of the T4-treated rats.

Energy and Antioxidant Status of Rat Liver Mitochondria during Hypoxia- Reoxygenation of Different Duration

2016 ◽  
Vol 7 (4) ◽  
pp. 349-361
Author(s):  
Olga A. Gonchar ◽  
Valentina I. Nosar ◽  
Larisa. V. Bratus ◽  
I. N. Tymchenko ◽  
N. N. Steshenko ◽  
...  
Keyword(s):  
Rat Liver ◽  
Antioxidant Status ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Hypoxia Reoxygenation
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