Specific Activity Of Cytochrome Oxidase Research Articles

Effects of transitory maternal pteroylglutamic acid (PGA) deficiency on respiratory control ratios, phosphorylative capacity, and cytochrome oxidase activities of mitochondria from rat embryos.

AbstractCytochrome oxidase activities and protein contents of homogenates and mitochondrial fractions of embryos from untreated and 9‐methyl PGA treated pregnant rats were determined on various days of gestation. Rates of respiration, ADP:O, and respiratory control ratios were determined with the mitochondrial fractions. The cytochrome oxidase specific activities of homogenates or mitochondrial fractions of treated embryos were similar to those of controls of the same age. However, total mitochondrial protein and cytochrome oxidase activities of the treated embryos were similar to those of controls even though the treated embryos were smaller than controls. The amount of oxygen consumed by the treated embryos was not significantly different from that consumed by controls and the ADP:O and respiratory control ratios calculated for mitochondrial fractions of treated and control embryos were not significantly different.

Lysosomal enzymes in aquatic species—II. Distribution and particle properties of thermally acclimated muscle lysosomes of rainbow trout, Salmo gairdneri

1. 1. Subcellular particles demonstrated structure-linked latent activity and single peak optimum activity in the acid pH range. 2. 2. Maximum activity of each acid hydrolase at different incubation temperatures varied from one enzyme to another. 3. 3. At 28°C incubation temperature there was greatest stability of all the acid hydrolases. 4. 4. The specific activity of cytochrome oxidase was significantly higher at cold thermal regimens. 5. 5. After differential centrifugation the highest relative specific activity of the enzymes was always found in the light mitochondrial fraction regardless of acclimation temperature.

Differences in cytochrome oxidase and mitochondrial ATPase in melanotic and amelanotic melanoma.

This paper deals with a description of the isolation and purification of mitochondria and melanosomes from Harding-Passey melanoma and mitochondria from Fortner melanoma together with a characterization of their cytochrome oxidase and membrane bound ATPase. In the melanotic tumor (Harding-Passey) the specific cytochrome oxidase activity was low in comparison to the enzymatic activity in the amelanotic tumor (Fortner) and in liver. The enzyme from the melanotic tumor could be inhibited only 30% by hydroxylamine, a specific inhibitor of the heme component of cytochrome oxidase, whereas the enzyme in the amelanotic tumor was inhibited by as much as 98%. This low hydroxylamine sensitivity concomitant with the low specific activity is due to a defective cytochrome oxidase in the melanotic melanoma. Similar results were obtained for membrane-bound ATPase. The enzyme from the amelanotic tumor was inhibited by oligomycin and also by an intrinsic inhibitor present in the mitochondria, whereas neither inhibitor had an effect on the ATPase from the melanotic tumor. From these results it may be concluded that the mitochondria from the amelanotic melanoma are functionally intact whereas the mitochondria from the melanotic melanoma are significantly altered or degenerated with respect to cytochrome oxidase and mitochondrial ATPase.

Distribution of α-tocopherol in beef heart mitochondria

1. α-Tocopherol was identified and determined in purified bovine heart mitochondria by several independent procedures including thin-layer chromatography, silicic acid column chromatography, gas-liquid chromatography and spectral examination. 2. The concentration of tocopherol in purified mitochondrial preparations ranged from 0.05 to 0.44 μmole of tocopherol per g of protein, and appeared to be independent of the specific activity of cytochrome oxidase in the same samples. 3. α-Tocopherol was found to be present in all the enzymatically active lipoprotein complexes of the electron transport system of mitochondria, but apparently did not have a direct quantitative relationship with the enzymatic activities observed. The highest concentration of tocopherol per g of protein occurred in a supernatant fraction free of any electron transport chain activity. 4. The subcellular fractions of beef heart muscle were examined for vitamin E content, and the crude nuclear fraction showed a considerable amount of tocopherol per g of protein. The supernatant fraction obtained after sedimentation of the mitochondria had very little vitamin E. 5. Separation of the mitochondrial membranes by digitonin treatment showed that only the inner membranes contained tocopherol.

Mitochondrial enzyme activity in “senescent” and virus-transformed human fibroblasts

The possible role of changes in mitochondrial content in limiting the in vitro lifespan of human fibroblasts in culture and on the cell line permanence engendered by virus transformation was evaluated. The specific activity of a mitochondrial enzyme, cytochrome oxidase, was determined in a normal human fibroblast strain from shortly after its in vitro cultivation to the cessation of division. Enzyme specific activity was also determined in an SV40-transformed permanent human fibroblast line. No age-dependent reduction in cytochrome oxidase specific activity was found in “senescent” human fibroblasts, nor was the specific activity of virus-transformed human fibroblasts significantly different than that of non-transformed cells. These data argue against changes in mitochondrial content as the basis for the limited in vitro lifespan of normal human fibroblasts, or for the cell line permanence of virus-transformed human fibroblasts.

Enzymes of the accessory boring organ of the muricid gastropod Urosalpinx cinerea follyensis. I. Aerobic and related oxidative systems.

1. Histochemical observations of the aerobic metabolism of the accessory boring organ (ABO) of Urosalpinx showed that cytochrome oxidase, succinate dehydrogenase and lactate dehydrogenase activities are localized in the secretory cells of the distal secretory disk.2. Correlated biochemical assays of cytochrome oxidase activity of whole homogenates of the ABO prepared from active snails gave specific activities which ranged between 0.190 to 2.10.3. There were no differences in cytochrome oxidase specific activities using ABO whole homogenates from resting or drilling snails. However, the specific activities of mitochondrial-rich particulate fractions isolated from whole homogenates by high speed centrifugation showed that oxidase activities of drilling specimens were 1.040 as opposed to 0.639 for samples from resting specimens.4. Snails did not bore shells of the oyster Crassostrea virginica when maintained in a N2 atmosphere, and ceased boring begun prior to transfer to anaerobic conditions.5. These data and observations were discussed in relation to physiological and ecological factors involved in predation and demineralization activities by Urosalpinx.

Enzyme patterns in isolated mitochondria from embryonic and larval tissues of Xenopus

The specific activities of cytochrome oxidase, ATPase, acid phosphatase, and cathepsin in homogenates of embryonic and larval tissues of Xenopus and in mitochondria derived from them have been determined. In all cases, determinations of enzyme activity were made on homogenates and mitochondria from early whole embryos, from tissue primordia, and from the fully differentiated end products of the primordia. The mitochondria from each embryonic or larval tissue studied have distinctive characteristics which appear as significant quantitative differences in specific activity of each of the four enzymes tested. During development, the changes in activity of each enzyme in the mitochondria from a given tissue follow an individual pattern which is independent of the pattern of other enzymes in the same mitochondria. In the case of cytochrome oxidase, a correlation has been found between the fine structure of the mitochondria and the level of enzymatic activity. Liver mitochondria have few cristae and relatively low specific activity of cytochrome oxidase; muscle mitochondria have numerous cristae and a high specific activity of cytochrome oxidase.

Studies on the electron transport system: XXXIX. Assay of cytochrome oxidase. Effect of phospholipids and other factors

Various phospholipid sols increase the specific activity of cytochrome oxidase when added to the assay medium and act primarily by retarding or preventing the aggregation of cytochrome oxidase particles. Aggregates of the enzyme cannot be dispersed by phospholipids although bile salts and sonic oscillation are effective. Reaction velocities obtained with the manometric, polarographic, and spectrophotometric assays can be brought into agreement by including phospholipid sols in the assay media and by extrapolating the specific activities to infinite concentration of cytochrome c. Inhibition of the reaction by cytochrome c is discussed.

Seasonal and starvation-induced changes in enzymatic pattern of frog nephron

Oxidative and hydrolytic enzyme activities in the nephron of the frog were investigated using histochemical and spectrophotometric techniques. The distal tubule was found to possess high activities of enzymes of glycolysis and the Krebs cycle, as well as high cytochrome oxidase activity, but had only slight activities of the hexose-monophosphate shunt enzymes. The proximal tubule had high activities of glycolytic enzymes, enzymes of the hexose-monophosphate shunt, and enzymes of the Krebs cycle, except for succinic dehydrogenase, which was present in very low activity. Proximal tubular cytochrome oxidase was found to vary according both to the season and to environ mental conditions. In freshly caught summer frogs it was present in high activity, but in winter frogs or summer frogs starved for periods of 10–30 days, no proximal tubular cytochrome oxidase could be detected, although other proximal tubular enzyme activities remained unchanged as far as could be histochemically determined. The specific activity of cytochrome oxidase in mitochondrial fractions was found to decrease by about 50% in the kidneys of starved and winter frogs, as compared with summer frogs.