The respiratory activity and permeability of housefly sarcosomes

Some properties of mitochondria isolated from the flight muscle of the periodical cicada, Magicicada septendecim

Mitochondria from the flight muscle of the periodical cicada oxidize pyruvate and d-glycerol 1-phosphate at rates comparable with those obtained with flight-muscle mitochondria from other insects. The oxidation of d-glycerol 1-phosphate is greatly stimulated by low concentrations of Ca(2+). However, oxidative phosphorylation with this substrate is optimum over only a narrow range of Ca(2+) concentration, because of the ability of these mitochondria actively to accumulate Ca(2+) present at micromolar concentrations. The oxidation of pyruvate via the complete tricarboxylic acid cycle is enhanced by high concentrations of phosphate. When both pyruvate and d-glycerol 1-phosphate are present simultaneously, there is no simple summation of the rates obtained with the substrates singly. Acetyl-l-carnitine, palmitoyl-l-carnitine, glutamate and 2-oxoglutarate are oxidized at rates similar to those obtained with mammalian mitochondria, though lower than those obtained with the two prime substrates. However, no other tricarboxylic acid-cycle intermediates added to the medium were oxidized. From these and other observations it has been concluded that these mitochondria possess a previously undescribed combination of substrate-anion permeases.

Specificity and locale of the L-3-glycerophosphate-flavoprotein oxidoreductase of mitochondria isolated from the flight muscle of Sarcophaga barbata thoms

1. The oxidation of l-3-glycerophosphate by flight-muscle mitochondria isolated from the flesh fly Sarcophaga barbata has been studied. Use of substrate analogues indicates that the catalytic and effector l-3-glycerophosphate binding sites on the allosteric l-3-glycerophosphate-flavoprotein oxidoreductase differ markedly in specificity. 2. The l-3-glycerophosphate-cyanoferrate oxidoreductase system in these mitochondria is antimycin-insensitive whereas the corresponding NADH-cyanoferrate oxidoreductase is extremely sensitive to this respiratory-chain inhibitor. Also no swelling is observed when these mitochondria are suspended in iso-osmotic solutions of ammonium glycerophosphate in contrast with the extensive swelling seen in similar solutions of ammonium pyruvate. These observations indicate that l-3-glycerophosphate does not penetrate the mitochondrial matrix whereas pyruvate does. 3. Submitochondrial particles catalyse the ATP-driven reduction of NAD(+) by l-3-glycerophosphate but at a far lower rate than that seen when succinate is the electron donor. These particles do not have an energy-linked pyridine nucleotide transhydrogenase activity. 4. We conclude that the l-3-glycerophosphate-flavoprotein oxidoreductase is located on the outer surface of the inner membrane of the flight-muscle mitochondria.

The carnitine-independent oxidation of palmitate plus malate by moth flight-muscle mitochondria

Mitochondria isolated from the flight muscle of the southern armyworm moth, Prodenia eridania, can oxidize palmitate+malate very rapidly. Added carnitine had no effect on the rate of oxidation of palmitate+malate by flight-muscle mitochondria from two species of moths, and carnitine palmitoyltransferase could not be detected in Prodenia by direct assay. Palmitoylcarnitine was not oxidized by moth mitochondria, but when added in low concentrations it reversibly suppressed the oxidation of palmitate. The evidence indicates that carnitine is not involved in fatty acid degradation by moth flight muscle. Added thiols, including CoA, also suppressed palmitate+malate oxidation. An ATP-dependent fatty acyl-CoA synthetase is present in moth mitochondria.

Tetrachloroanisol: a source of musty taste in eggs and broilers

Ingestion by hens and broilers of specific chloroanisols present in some wood shavings used in poultry cages can result in a musty taste in poultry products.

Pyruvate oxidation and the permeability of mitochondria from blowfly flight muscle

The rate of pyruvate oxidation by mitochondria from blowfly flight muscle decreased in the presence of tris (hydroxymethyl) aminomethane (Tris). An increase in the rate of mitochondrial swelling was concomitant with the loss of pyruvate oxidation. These changes were prevented by bovine serum albumin, adenosine triphosphate, and magnesium ions, factors required for mitochondrial contraction. Proline, but not glutamate or malate, restored the rate of pyruvate oxidation to original values. These findings suggest that mitochondrial swelling leads to leakage of intramitochondrial intermediates of the Krebs cycle, accounting for the decrease in the rate of pyruvate oxidation. Exogenous proline penetrates the mitochondrial membrane and is rapidly oxidized, via glutamate, forming intramitochondrial precursors of oxaloacetate. Malate and glutamate were ineffective because of the selective permeability of the mitochondrial membrane.

The components of an alpha-glycerophosphate cycle and their relation to oxidative metabolism in the lens

1. The concentration of ATP in a lens brei is maintained when the brei is incubated in oxygen with alpha-glycerophosphate. Lack of alpha-glycerophosphate or incubation in nitrogen causes the concentration to decrease. alpha-Glycerophosphate has some effect under anaerobic conditions but this is not sufficient to account for the maintenance in oxygen. 2. Manometric experiments show that alpha-glycerophosphate enhances the respiration of lens preparations. This respiration can be further increased by the addition of ADP and is abolished by cyanide and antimycin. The inference from these experiments is that a mitochondrial system able to oxidize alpha-glycerophosphate is present, i.e. the particulate half of the alpha-glycerophosphate cycle. 3. More than the calculated proportion of NADH is used when limiting amounts of dihydroxyacetone phosphate are added to lens tissue in spectrophotometric experiments. Dihydroxyacetone phosphate is therefore regenerated and an alpha-glycerophosphate cycle is operative. 4. A preparation of a particulate alpha-glycerophosphate dehydrogenase that takes up oxygen with methylene blue as electron acceptor is described. 5. Methods for obtaining mitochondria from lens are compared, and a useful extraction medium is defined. 6. Mitochondria with activities of the same order of magnitude as those obtained from liver, with alpha-glycerophosphate and glutamate as substrates, are prepared from epithelium detached from the capsule; some respiratory control is observed.