scholarly journals FURTHER OBSERVATIONS ON THE PRODUCTION OF AMINO ACIDS BY RAT-LIVER MITOCHONDRIA AND OTHER SUBCELLULAR FRACTIONS

1965 ◽  
Vol 95 (3) ◽  
pp. 641-656 ◽  
Author(s):  
KGMM ALBERTI ◽  
W BARTLEY
Keyword(s):  
Amino Acids ◽  
Rat Liver ◽  
Liver Mitochondria ◽  
Subcellular Fractions ◽  
Rat Liver Mitochondria

Comparative studies of CDP-diacylglycerol synthase in rat liver mitochondria and microsomes

1993 ◽  
Vol 71 (3-4) ◽  
pp. 183-189 ◽  
Author(s):  
Amy Y. P. Mok ◽  
Gordon E. McDougall ◽  
William C. McMurray
Keyword(s):  
Phosphatidic Acid ◽  
Rat Liver ◽  
Mitochondrial Fraction ◽  
Liver Mitochondria ◽  
Subcellular Fractions ◽  
Rat Liver Mitochondria ◽  
Mitochondrial Enzyme ◽  
Egg Lecithin ◽  
Microsomal Membranes ◽  
Concentration Curves

CDP-diacylglycerol for polyglycerophosphatide biogenesis can be synthesized within rat liver mitochondria. Contamination by microsomal membranes cannot account for the CDP-diacylglycerol synthesis found in the mitochondria. Phosphatidic acid from egg lecithin was the best substrate for the synthesis of CDP-diacylglycerol in both subcellular fractions. Concentration curves for CTP and Mg2+ differed for the two subcellular fractions. Microsomal CDP-diacylglycerol synthase was specifically stimulated by the nucleotide GTP; this stimulatory effect by GTP was not observed in the mitochondrial fraction. By comparison, the microsomal enzyme was more sensitive towards sulfhydryl inhibitors than the mitochondrial enzyme. The enzymes could be solubilized from the membrane fractions using 3-[(cholamidopropyl)dimethylammonio]-1-propanesulfonate, and the detergent-soluble activity could be partially restored by addition of phospholipids. Based on the differences in properties, it was concluded that there are two distinct enzyme localizations for CDP-diacylglycerol synthesis in mitochondria and microsomes from rat liver.Key words: CDP-diacylglycerol, synthase, phosphatidic acid, mitochondria, microsomes, solubilization.

Biosynthesis of phosphatidic acid by glycerophosphate acyltransferases in rat liver mitochondria and microsomes

1990 ◽  
Vol 68 (12) ◽  
pp. 1380-1392 ◽  
Author(s):  
Amy Y. P. Mok ◽  
William C. McMurray
Keyword(s):  
Phosphatidic Acid ◽  
Rat Liver ◽  
Neutral Lipids ◽  
Divalent Cations ◽  
Liver Mitochondria ◽  
Fatty Acyl ◽  
Subcellular Fractions ◽  
Rat Liver Mitochondria ◽  
Acyl Donor ◽  
Palmitoyl Carnitine

The acyltransferases that catalyze the synthesis of phosphatidic acid from labelled sn-[14C]glycero-3-phosphate and fatty acyl carnitine or coenzyme A derivatives have been shown to be present in both isolated mitochondria and microsomes from rat liver. The major reaction product was phosphatidic acid in both subcellular fractions. A small quantity of lysophosphatidic acid and neutral lipids were produced as by-products. Divalent cations had significant effects on both mitochondrial and microsomal fractions in stimulating acylation using palmitoyl CoA, but not when palmitoyl carnitine was used as the acyl donor. Palmitoyl CoA and palmitoyl carnitine could be used for acylation by both mitochondria and microsomes. Mitochondria were more permeable to palmitoyl carnitine and readily used it as the substrate for acylation. On the other hand, microsomes yielded a better rate with palmitoyl CoA and the rate of acylation from palmitoyl carnitine in microsomes was correlated with the degree of mitochondrial contamination. The enzymes were partially purified from Triton X-100 extracts of subcellular fractions. Based on the differences of substrate utilization, products formed, divalent cation effects, molecular weights, and polarity, the mitochondrial and microsomal acyltransferases appeared to be different enzymes.Key words: glycerophosphate, acyltransferase, mitochondria, microsomes, phosphatidic acid.

scholarly journals The localization of proteolytic activity in rat liver mitochondria and its relation to mitochondrial swelling and aging

1969 ◽  
Vol 111 (5) ◽  
pp. 763-776 ◽  
Author(s):  
K. G. M. M. Alberti ◽  
W. Bartley
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Proteolytic Activity ◽  
Rat Liver ◽  
Acid Production ◽  
Liver Mitochondria ◽  
Ground Substance ◽  
Rat Liver Mitochondria ◽  
Amino Acid Production ◽  
Freezing And Thawing

1. On storage of rat liver mitochondria at 0°, water content, total amino acid content and leakage of protein all rose steadily over a 72hr. period. The initial ratio of intramitochondrial to extramitochondrial amino acid concentration lay between 18 and 24. Initially this rose, but it then fell to 1·9 at the end of storage. The concentration gradient between internal and external amino acids was relatively constant throughout the period. These processes were accentuated at 22° and 40°, the concentration gradient reaching 70μmoles/ml., water content rising to 8·3mg./mg. dry wt. and protein leakage reaching 42% of total mitochondrial protein. ‘Swelling agents’ produced no correlated changes in amino acid production and swelling. 2. Added glutamate was not concentrated within the pellet of whole or disrupted mitochondria. Endogenous amino acids were distributed evenly between the pellet and the supernatant of disrupted mitochondria. It is concluded that amino acids are produced within mitochondria and that adsorption and uptake from the medium do not contribute significantly to amino acids in the pellet. 3. β-Glycerophosphate, a lysosome protectant, increased amino acid production by rat liver mitochondria. Treatment with Triton X-100 and disruption by freezing and thawing showed that 56% of proteolytic activity was ‘free’ in whole mitochondria, whereas only 11% of acid phosphatase activity, a lysosomal enzyme, was ‘free’. 4. ‘Light’ mitochondria contained 30% more neutral proteolytic activity but 300% more acid phosphatase activity than ‘heavy’ mitochondria. 5. Electron micrographs of mitochondrial preparations showed less than one particle in 500 that could be identified as a lysosome. Treatment with Triton X-100 disrupted the structure of roughly 50% of the mitochondria; the rest appeared to retain their membrane, cristae and ground substance. Freezing and thawing caused gross swelling and loss of ground substance and rupture of external membranes. 6. Of the recovered proteolytic activity, 81% at pH7·4 and 70% at pH5·8 were found in the high-speed supernatant of broken mitochondria. A further fivefold increase in specific activity was found in the first protein fraction obtained by Sephadex G-50 gel filtration. 7. Between 60 and 80% of proteolytic activity was found in the 40–60%-saturated ammonium sulphate precipitate. Almost all of the soluble-fraction proteolytic activity could be recovered in a pH5·0 supernatant. 8. The results give no support to the view that mitochondrial neutral proteolytic activity reflects lysosomal content. 9. The possible role of intramitochondrial amino acid production and the proteolysis of internal barriers in passive swelling of mitochondria is discussed.

Transamination of Ring-Substituted L-Phenylalanines by an Extract from Rat Liver Mitochondria

1973 ◽  
Vol 51 (4) ◽  
pp. 407-411 ◽  
Author(s):  
J. H. Tong ◽  
B. A. Stoochnoff ◽  
A. D'Iorio ◽  
N. Leo Benoiton
Keyword(s):  
Amino Acids ◽  
Rat Liver ◽  
Liver Mitochondria ◽  
Tyrosine Aminotransferase ◽  
Rat Liver Mitochondria ◽  
Amino Group ◽  
Mitochondrial Enzyme ◽  
Soluble Enzyme ◽  
Keto Acids ◽  
Mitochondrial Extract

The L- and D-isomers of m-tyrosine, o-tyrosine, p-chlorophenylalanine (p-CP), and p-fluorophenylalanine (p-FP) were tested as substrates for the soluble tyrosine aminotransferase and a mitochondrial extract of rat liver by measuring the amino acids formed with 2-oxoglutarate, oxaloacetate, and pyruvate as acceptors. None of the above were substrates for the soluble enzyme. L-m-Tyrosine, L-p-CP, and L-p-FP were transaminated at substantial rates (16–25% of the rate for L-tyrosine) by the mitochondrial enzyme with all three keto acids as amino group acceptors. A slow but definite transamination of L-o-tyrosine by the mitochondrial enzyme was demonstrated using labeled 2-oxoglutarate as acceptor.

Different Effect Of Dgtp On 2'-Deoxyadenosine Metabolism In Mitochondria And Cytosol

1992 ◽  
Vol 47 (11-12) ◽  
pp. 893-897 ◽  
Author(s):  
Janusz Greger ◽  
Fabianowska-Majewska Krystyna
Keyword(s):  
Physical Properties ◽  
Adenosine Deaminase ◽  
Rat Liver ◽  
Liver Mitochondria ◽  
Subcellular Fractions ◽  
Rat Liver Mitochondria

Two enzymes participating in 2′-deoxyadenosine (dAdo) metabolism: dAdo kinase (dAdoK EC 2.7.1.76) and adenosine deaminase (ADA, EC 3.5.4.4) were partially purified from rat liver mitochondria and cytosol and influence of nucleosides and nucleotides on the activity of these enzymes were investigated. Mitochondrial and cytosol dAdoK are separate proteins, while ADA from both subcellular fractions possesses similar physical properties. dGTP, a com petitive inhibitor of mitochondrial dAdoK, inhibits cytosol ADA in a mixed way but activates mitochondrial ADA and cytosol dAdoK. A possible effect of dGTP on dAdo metabolism in mitochondria and cytosol is discussed

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