Restoration Of Enzyme Activity Research Articles

The influence of fatty acid composition on the restoration of succinate-cytochrome c reductase activity by phospholipids in extracted mitochondria

1. 1.|The requirement of the electron transport chain for phospholipids, previously shown for beef heart mitochondria, has been confirmed for rat liver mitochondria. The succinate-cytochrome c reductase activity of mitochondria whose lipids had been extracted with acetone has been restored by incubating with micelles of phospholipids. 2. 2.|Phospholipids that differ only in their fatty acid composition have been prepared from the livers of normal rats and rats deficient in essential fatty acids. 3. 3.|Restoration of enzyme activity was, within limits, proportional to the amount of phospholipid bound by mitochondrial protein and, once bound, phospholipids from normal and deficient rats were equally effective. However, the rate of binding could be influenced by the fatty acid composition of the phospholipids. 4. 4.|It is suggested that enzymes of the electron transport chain do not have any special requirement for phospholipids that contain essential fatty acids.

The effect of α-tocopherol on essential fatty acid oxidation in liver mitochondria from vitamin E-deficient chicks

Development of encephalomalacia in chicks seemed related to the depression of enzymic activity in the liver mitochondria. If injected intramuscularly at the first sign of symptoms, α-tocopherol alleviated the symptoms and restored enzyme activity. Furthermore, the liver mitochondria obtained from chicks which had received injections of α-tocopherol was not subject to peroxidation to any greater degree than the liver mitochondria obtained from chicks which had been kept on a vitamin E-supplemented diet. Lipid peroxidation was found to coincide with linoleate oxidation in the liver mitochondria of vitamin E-deficient chicks. The lipoperoxides seemed to inhibit coupling of an enzyme with cytochrome c and cytochrome a in the electron-transport system.

Effect of epinephrine on phosphorylase and glycogen levels in the rat uterus.

An intraperitoneal injection of eipinephrine into spayed rats, treated with estradiol benzoate 48 hr before, decreased uterine phosphorylase α (active) activity and glycogen concentration slightly within 5 min and to a minimum within 30–60 min. The restoration of enzyme activity occurred abruptly between the 2nd and 3rd hr, but the recovery of glycogen was gradual and was attained approximately at the 8th hour. Spayed rats were treated with estradiol and epinephrine concurrently, and with additional epinephrine at intervals for 6 hr. Others received only estradiol or no treatment. Epinephrine inhibited the effects of estradiol to increase uterine weight, phosphorylase a activity and glycogen deposition. Epinephrine also produced uterine vasoconstriction. Interruption of the uterine blood supply in estrogenprimed rats for 10 min caused a decrease in phosphorylase a activity and in glycogen concentration similar to that observed 15 min after treatment with epinephrine. From these observations and others, it...

A specific antidote against lethal alkyl phosphate intoxication. IV. Effects in brain

The recovery of acetylcholinesterase activity in brain following injection of alkyl phosphates (DFP, paraoxon, and OMPA) has been studied without and in combination with PAM. Whole brains of mice were used throughout the experiments. 1. For the evaluation of the enzyme activity in the intact cell during lifetime, a procedure has been used in which the tissue has been extracted with chloroform. The values obtained with this method were much higher during the first 24-hr. period than in homogenized tissue without chloroform extraction. This result indicates that considerable amounts of alkyl phosphate must be present, during the 24-hr. period following injection, in the extracellular fluid and in lipide, unable to reach the intracellular esterase. After that period of time no measurable difference was found between the two techniques; apparently all the extracellular alkyl phosphate had been removed. The new method proved to be greatly superior compared to those previously used for evaluating intracellular enzyme activity during life. 2. The esterase activity after LD 50 of paraoxon is about 25–30% of the initial, whether the animal dies or survives. The activity after injection of DFP is much lower than that after injection of paraoxon, about 5% of the initial. The rate of recovery is slow and not markedly different whether DFP or paraoxon is used. 3. After injection of 35 mg./kg. of OMPA, which is close to a sure lethal dose, inhibition of only 10% was found. 4. In contrast to the marked rise of enzyme activity in diaphragm following the administration of PAM, no effect of this compound is detectable on the enzyme activity in brain with amounts which protect the animal against death. Only by repeated injections of PAM, a 25 % increase of enzyme activity was found following injection of paraoxon; when DFP was used no clear-cut reactivation by PAM was observed, even after repeated injections. These results indicate that PAM in concentrations adequate to preserve life does not readily penetrate into the brain. Since, however, whole brains were used for the determinations, the experiments do not exclude that in some parts of the brain PAM restored enzyme activity important for survival. 5. The availability of PAM makes it possible to apply much higher amounts of DFP or paraoxon compatible with life than ever used before. Therefore, the minimum enzyme activity in brain compatible with life has been determined with extreme doses. Repeated injections of LD 50 of either DFP or paraoxon did not seem to influence markedly the concentration as compared with the first injection. However, after a single very high dose of DFP (50 mg./kg., i.e., about 12-fold LD 50 ) against which PAM in combination with atropine is still able to protect, the hydrolytic activity was found to be 2.4 mg./g./hr. or about 2% of the initial. This value was found at the peak of inhibition. Two hours later, the value was about doubled. The significance of these findings is discussed.

Dihydrostreptomycin inhibition of cysteine desulfhydrase in cell free extracts of Escherichia coli.

Summary1) The effect of streptomycin on the cysteine desulfhydrase in cell free extracts of E. coli is reported. 2) 2.5 μg of streptomycin/1 mg of crude extract protein caused almost complete inhibition of enzyme activity. 3) Inhibition is of a non-competitive type, since it is not reversed by increasing concentrations of substrate. 4) Inhibition is irreversible, since the removal of streptomycin by prolonged dialysis did not cause a restoration of enzyme activity.

A tissue factor influencing succinic dehydrogenase activity in tuberculous guinea pigs.

The alterations in succinic dehydrogenase activity during the course of infection with Mycobacterium tuberculosis strains H37Rv and BCG, as well as with dead bacilli, has been described. A tissue factor has been described which is prepared from normal bovine kidney and will restore enzyme activity in vitro. This factor is prepared by chromatographic analysis and contains a nucleotide with an ultraviolet absorption maxima at 250 mmicro (pH 3) and a free sulfhydryl group. The role of this factor in the response to tuberculosis is discussed.