scholarly journals Cytochrome c oxidase is preferentially synthesized in the rough endoplasmic reticulum-mitochondrion complex in rat liver

1982 ◽  
Vol 208 (2) ◽  
pp. 505-507 ◽  
Author(s):  
S Parimoo ◽  
N Rao ◽  
G Padmanaban
Keyword(s):  
Endoplasmic Reticulum ◽  
Cytochrome C ◽  
Cytochrome Oxidase ◽  
Cytochrome C Oxidase ◽  
Rat Liver ◽  
Rough Endoplasmic Reticulum ◽  
Specific Activity ◽  
Mitochondrial Fraction

The specific activity and content of cytochrome oxidase in the rough endoplasmic reticulum-mitochondrion complex are higher than in the mitochondrial fraction. Radiolabelling studies with the use of hepatocytes and isolated microsomal and rough endoplasmic reticulum-mitochondrion fractions, followed by immunoprecipitation with anti-(cytochrome oxidase) antibody, reveal that the nuclear-coded cytoplasmic subunits of cytochrome oxidase are preferentially synthesized in the latter fraction. The results have a bearing on the mechanism of transport of these subunits into mitochondria.

scholarly journals Two fractions of rough endoplasmic reticulum from rat liver. I. Recovery of rapidly sedimenting endoplasmic reticulum in association with mitochondria.

1977 ◽  
Vol 72 (3) ◽  
pp. 714-725 ◽  
Author(s):  
G C Shore ◽  
J R Tata
Keyword(s):  
Endoplasmic Reticulum ◽  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Rat Liver ◽  
Rough Endoplasmic Reticulum ◽  
Structural Damage ◽  
Gradient Centrifugation ◽  
Mitochondrial Protein ◽  
Enzyme Analysis ◽  
Marker Enzyme

Low-speed centrifugation (640 g) of rat liver homogenates, prepared with a standard ionic medium, yielded a pellet from which a rapidly sedimenting fraction of rough endoplasmic reticulum (RSER) was recovered free of nuclei. This fraction contained 20-25% of cellular RNA and approximately 30% of total glucose-6-phosphatase (ER marker) activity. A major portion of total cytochrome c oxidase (mitochondrial marker) activity was also recovered in this fraction, with the remainder sedimenting between 640 and 6,000 g. Evidence is provided which indicates that RSER may be intimately associated with mitochondria. Complete dissociation of ER from mitochondria in the RSER fraction required very harsh conditions. Sucrose density gradient centrifugation analysis revealed that 95% dissociation could be achieved when the RSER fraction was first resuspended in buffer containing 500 mM KCl and 20 mM EDTA, and subjected to shearing. Excluding KCl, EDTA, or shearing from the procedure resulted in incomplete separation. Both electron microscopy and marker enzyme analysis of mitochondria purified by this procedure indicated that some structural damage and leakage of proteins from matrix and intermembrane compartments had occurred. Nevertheless, when mitochondria from RSER and postnuclear 6,000-g pellet fractions were purified in this way fromanimals injected with [35S]methionine +/- cycloheximide, mitochondria from the postnuclear 6,000-g pellet were found to incorporate approximately two times more cytoplasmically synthesized radioactive protein per milligram mitochondrial protein (or per unit cytochrome c oxidase activity) than did mitochondria from the RSER fraction. Mitochondria-RSER associations, therefore, do not appear to facilitate enhanced incorporation of mitochondrial proteins which are newly synthesized in the cytoplasm.

scholarly journals Canine submandibular-gland hyaluronidase. Identification and subcellular distribution

1968 ◽  
Vol 110 (1) ◽  
pp. 9-17 ◽  
Author(s):  
Y. H. Tan ◽  
J. M. Bowness
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Submandibular Gland ◽  
High Speed ◽  
Specific Activity ◽  
Mitochondrial Fraction ◽  
Product Formation ◽  
Triton X ◽  
Submandibular Saliva ◽  
Testicular Hyaluronidase

1. Submandibular glands from four species of mammal have been shown to contain a hyaluronidase active at acid pH; glands from dog and cat had a much higher content of this enzyme than has been found in other sources. 2. Product formation from hyaluronate after 24hr. incubation was almost the same as with testicular hyaluronidase, indicating that the enzyme is an endo-poly-β-hexosaminidase. 3. When submandibular-gland homogenates were fractionated by the scheme developed for liver by de Duve, Pressman, Gianetto, Wattiaux & Appelmans (1955), all the enzymes assayed, except cytochrome c oxidase, were found to occur partly in the soluble fraction and partly in the particulate fractions. Among the particular fractions, the highest specific activity was found in the heavy-mitochondrial fraction for cytochrome c oxidase, in the microsomal fraction for alkaline phosphatase and in the light-mitochondrial fraction for acid phosphatase, β-N-acetylhexosaminidase and acid-active hyaluronidase. 4. Release of the enzyme activity from the sedimentable fractions occurred in 0·1% Triton X-100 or after high-speed homogenization. 5. Stimulation of dogs by pilocarpine was found to decrease the hyaluronidase content of the submandibular gland by 5% and to cause the occurrence of a corresponding amount of acid-active hyaluronidase in the submandibular saliva. 6. The results are discussed in relation to the subcellular localization of hyaluronidase.

scholarly journals Kinetics of inhibition of purified and mitochondrial cytochrome c oxidase by psychosine (β-galactosylsphingosine)

1993 ◽  
Vol 290 (1) ◽  
pp. 139-144 ◽  
Author(s):  
C E Cooper ◽  
M Markus ◽  
S P Seetulsingh ◽  
J M Wrigglesworth
Keyword(s):  
Cytochrome C ◽  
Cytochrome Oxidase ◽  
Cytochrome C Oxidase ◽  
Rat Liver ◽  
Liver Mitochondria ◽  
Slow Phase ◽  
Rat Liver Mitochondria ◽  
Mitochondrial Cytochrome ◽  
Submitochondrial Particles ◽  
Bovine Heart

1. Psychosine (beta-galactosylsphingosine) is the toxic agent in Krabbe's disease (globoid cells leukodystrophy). It inhibits purified bovine heart mitochondrial cytochrome c oxidase; there is a rapid phase of inhibition (complete within 10-15 s) and a slower phase (complete within 10-15 min). Both phases are also seen in rat liver mitochondria. IC50 is about 200 microM psychosine in the purified enzyme and less than 20 microM in mitochondria. Psychosine inhibition is due to binding to cytochrome oxidase, not cytochrome c. 2. Bovine heart submitochondrial particles show inhibition similar to rat liver mitochondria. However, although proteoliposomes containing bovine heart cytochrome oxidase show an identical fast phase, they have no noticeable slow phase of inhibition. Addition of phospholipid liposomes to submitochondrial particles relieved the majority of psychosine inhibition, consistent with the removal of those molecules binding in the slow phase. Psychosine can inhibit cytochrome oxidase molecules facing in either direction in proteoliposomes and submitochondrial particles, suggesting that it can rapidly interact with both sides of a membrane when added externally. 3. At high ionic strength, the presence of psychosine decreases the Vmax. of cytochrome oxidase with little effect on the Km for cytochrome c. This non-competitive inhibition suggests that the psychosine-enzyme complex is kinetically inactive and not labile over the time course of the assay. Psychosine does not inhibit the reduction of haem a or haem a3 by artificial electron donors, but does inhibit the reduction of haem a by cytochrome c.

The influence of chronic ethanol feeding to rats on liver mitochondrial membrane structure and function

1980 ◽  
Vol 58 (10) ◽  
pp. 1147-1155 ◽  
Author(s):  
E. A. Hosein ◽  
Hung Lee ◽  
Ilan Hofmann
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Rat Liver ◽  
Mitochondrial Membrane ◽  
Membrane Structure ◽  
Membrane Lipids ◽  
Specific Activity ◽  
Structure And Function ◽  
Membrane Structure And Function ◽  
And Function

Arrhenius plots were generated on the activity of rat liver mitochondrial cytochrome c oxidase from Metrecal–sucrose fed controls and Metrecal–alcohol fed experimentals. Chronic alcohol feeding resulted in diminished specific activity of cytochrome c oxidase and abolition of the discontinuity temperature at 17.5 °C found in the controls. Twenty-four hours after alcohol withdrawal, a discontinuity temperature reappeared at 14.4 °C; at 48 h it increased to 22.6 °C and returned to normal (17.4 °C) at 72 h. Such liver mitochondria also showed a decreased capacity to oxidize the acetyl group of acetyl carnitine immediately following prolonged alcohol feeding. When the assay was performed following withdrawal from alcohol 24 h later, oxidation was enhanced and this effect persisted for another 48 h. These latter results revealed a diminished capacity of such mitochondria to oxidize short chain fatty acids during alcohol feeding and the reverse during alcohol withdrawal.These results, complemented by thermographic data obtained through differential scanning calorimetry (DSC) reinforced the view that chronic alcoholic feeding induced adaptive changes in the fluidity of rat liver mitochondrial membrane lipids. Moreover, they demonstrated that in the microenvironment of the membrane-bound enzymes on withdrawal from ethanol, the membrane readapts to the new conditions without alcohol. This involved modulation of membrane structure and function and at the same time demonstrated a role for the membrane in the expression of tolerance and functional dependence on alcohol.

scholarly journals STUDIES ON THE BIOGENESIS OF SMOOTH ENDOPLASMIC RETICULUM MEMBRANES IN HEPATOCYTES OF PHENOBARBITAL-TREATED RATS

1974 ◽  
Vol 62 (3) ◽  
pp. 635-646 ◽  
Author(s):  
Joan A. Higgins
Keyword(s):  
Endoplasmic Reticulum ◽  
Cytochrome C ◽  
Rat Liver ◽  
Actinomycin D ◽  
Specific Activity ◽  
Smooth Endoplasmic Reticulum ◽  
Control Level ◽  
Phospholipid Synthesis ◽  
Protein Ratio ◽  
Nadph Cytochrome C Reductase

The specific activity of the acyltransferases of smooth microsomes of rat liver rose threefold by 12 h after injection of phenobarbital, while the activity of the acyltransferases of the rough microsomes rose slightly to peak at 3–4 h, and subsequently fell. The latter rise was abolished by treatment of the animal with actinomycin D or puromycin, while that of the smooth microsomes was unaffected. Incorporation of [14C]glycerol into phospholipid of smooth microsomes was elevated 100% by phenobarbital, while that of the rough microsomes was elevated 15%, and this could be accounted for by exchange between the microsomal phospholipids. The phospholipid/protein ratio of the smooth microsomes rose 1.5 times 3–4 h after injection of phenobarbital, while that of the rough microsomes fell slightly. The specific activity of NADPH cytochrome c reductase and NADPH diaphorase rose first in the rough microsomes, and subsequently in the smooth microsomes at a time coinciding with the return of the phospholipid/protein ratio to the control level. The rise in phospholipid/protein ratio was unaffected by actinomycin D or puromycin. These results indicate that the proliferating smooth membranes are the site of phospholipid synthesis, and that the phospholipid/protein ratio of these membranes may change independently.

Immunological and chemical characterization of rat liver cytochrome c oxidase

1981 ◽  
Vol 669 (2) ◽  
pp. 222-230 ◽  
Author(s):  
Peter Merle ◽  
Jochen Jarausch ◽  
Michael Trapp ◽  
Renate Scherka ◽  
Bernhard Kadenbach
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Rat Liver ◽  
Chemical Characterization ◽  
Liver Cytochrome
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