Superoxide dismutases (SOD) of high purity have been obtained from grey and white matter of bovine brain cerebral hemispheres. The SOD obtained have been shown to have three isoenzymes (a, b, c). A study of the catalytic and macromolecular properties of the SOD obtained from grey and white matter of cerebral hemispheres as well as their optical and electron paramagnetic resonance spectra indicates that both proteins possess similar properties. The possible function of SOD in grey and white matter of brain is discussed.

Animals↗

PubMed1976

[Molecular heterogeneity of rat brain and kidney glutamate dehydrogenase].

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Adenosine Diphosphate↗

PubMed1976

[Rat brain and liver glutamine synthetase and gamma-glutamyltransferase activity in alloxan diabetes (IV)].

Glutamine synthetase and gamma-glutamyltransferase activities of brain and liver homogenates of rats suffering from alloxan diabetes were determined in the soluble fraction (fraction 1) and in that obtained after treatment with 0.2 percent deoxycholate (fraction 2). The results obtained indicate that the activities of these enzymes in homogenates of brain and liver of diabetic animals does not differ from that of normal animals. gamma-Glutamyltransferase activity of brain is significantly reduced (about 5 fold) in the soluble fraction while glutamine synthetase activity is not much changed. The activities of glutamine-synthetase and gamma-glutamyltransferase of the 2-nd fraction obtained from rat brain and liver are very much higher than in the first fraction and are not considerably different from the activities observed in normal animals. In contrast to brain, glutamine synthetase and gamma-glutamyltransferase activities of liver of diabetic animals do not differ from the activities observed in normal animals, both in the homogenates and in the 1-st and 2-nd fractions.

Animals↗

PubMed1976

[New copper-containing protein from the brain].

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Animals↗

PubMed1975

[Effect of glutamic acid on the interrelationship of the effects of different activators of cerebral glutaminase].

When phosphate and tyroxine (activators of brain glutaminase) are used in small amounts, a potentiation of their stimulatory effect is observed. Higher concentrations exhibit an opposite effect. Glutamic acid has a strong inhibitory effect on all the activators of glutaminase given separately. The inhibitory effect of glutamate increases on lowering the pH. On the other hand the potentiation observed on adding two stimulators is increased greatly in the presence of glutamate. On the addition of tyroxine to other stimulators a greater potentiation and rise of glutaminase activity are observed. The potentiation, which occurs on the joint addition of phosphate and tyroxine, is raised with the increase of the amount of glutamic acid, while on the contrary on joining phosphate with other stimulators potentiation is reduced. Potentiation is variable and depends on the pH. Preincubation of brain mitochondrial fraction with guanidine chloride inhibits markedly the stimulatory effect of all the stimulators used, but their joint addition almost abolishes the potentiating effect. In the presence of glutamic acid, due to the increase of the cooperative effect between the two stimulators, glutaminase activity is greatly increased and sometimes its inhibitory effect is not even observed. The data obtained indicate that in brain glutamic acid in the presence of phosphate+thyroxine cannot be considered as an inhibitor of glutaminase and that the important factor here is not so much the absolute levels of the activators as their favorable combinations.

Animals↗

PubMed1975

[Role of adenine mono- and dinucleotides in ammonia formation in brain tissue].

The investigations carried out have shown that not only AMP but ADP also undergoes direct deamination in both soluble and mitochondrial fractions of rat brain tissue. Deamination of AMP is stimulated by the addition of ATP and the activity of one of the isoenzymes of AMP-aminohydrolase is markedly enhanced by both yeast and brain hexokinase. Activation by hexokinase is mainly due to its SH groups, through which hexokinase reacts with AMP-aminohydrolase, forming, probably, a protein-protein complex in which AMP aminohydrolase activity is considerably increased. Hexokinase does not affect the deamination of ADP and NAD. Further experiments are needed to find out whether the activation of AMP-aminohydrolase is accomplished by hexokinase itself or by an other protein contaminating it. Deamination of NAD, in contrast to AMP and ADP, takes place only in mitochondria and does not occur in the soluble fraction. In mitochondria besides deamination, AMP and ADP undergo intensive dephosphorylation, while the deamination of NAD is not accompanied by an increase of phosphate, i. e. mitochondria lack enzymes which breakdown NAD to mono nucleotides. Our data indicate that the formation of deamino -NAD from NAD and reamination of deamino-NAD by aspartate to NAD by the formation of intermediary NAD-succinate is of greater importance. The formation of the latter and that of deamino-NAD from NAD as well as the presence of preformed deamino-NAD in mitochondria have been demonstrated by Movsessian. The occurrence of these processes in mitochondria and their role in the formation of ammonia from amino acids is of importance in as much as oxaloacetate formation and its conversion to aspartate, which is necessary for the reamination of deamino-NAD, are localized in mitochondria. The main source of the amino nitrogen of aspartate is known to be glutamate, which incorporates the amino nitrogen of most amino acids. alpha-Keto-glutarate, which is necessary for the synthesis of glutamate, is also formed in mitochondria are the most favourable site for the formation of ammonia from amino acids with the participation of pyridine nucleotides. Of the purine mono and dinucleotides studied deamino-NAD is most effective in the formation of ammonia from amino acids in mitochondria since in contrast to purine mono nucleotides, deamino-NAD and NAD are not dephosphorylated in mitochondria. According to some authors the reamination of IMP by aspartate is of importance in the formation of ammonia from amino acids in brain tissue. In our studies, however, IMP was not effective in the formation of ammonia from aspartate in mitochondrial fractions. IDP was found to be more effective. IMP and IDP may probably participate in the formation of ammonia in the soluble fraction, where nucleotidase activity is considerably low.

AMP Deaminase↗

PubMed1975

[Soluble cerebral metalloproteins. 1. Purification and properties of cerebral cortex cytochrome c].

Cytochrome c from grey matter of brain has been obtained as a homogeneous preparation by electrophoresis on polyacrylamide gel and following electrofocusing in ampholine solutions. Its molecular weight, content of iron, redox potential and isoelectric point have been established. The absolute spectra of its oxidized and reduced forms are presented. Cytochrome c of brain cortex is similar in its properties to that obtained from other animal tissues as the heart and adrenal cortex.

Animals↗