Rat Brain Cytosol Research Articles

Acetoacetate and brain lipogenesis: developmental pattern of acetoacetyl-coenzyme A synthetase in the soluble fraction of rat brain.

The existence of acetoacetyl-CoA synthetase in rat brain cytosol is reported. The coupling of this enzyme with cytosolic acetoacetyl-CoA thiolase can provide acetyl-CoA for lipogenesis and cholesterol synthesis without the need for mitochondrial participation. This new route for acetoacetate utilization may be important in developing brain.

Protamine kinase independent of adenosine 3′,5′-monophosphate from rat brain cytosol

A protein kinase was obtained from rat brain cytosol which phosphorylated preferentially protamine and to some extent histone. This enzyme was independent of adenosine 3′,5′-monophosphate (cyclic AMP) and was not identical with the catalytic unit of cyclic AMP-dependent protein kinase. The enzyme and cyclic AMP-dependent protein kinase from this tissue were distinguishable from each other in their kinetic and catalytic properties, and phosphorylated different seryl and threonyl residues of protamine and histone.

DNA synthesis in isolated nuclei from the brains of rats at different post-partal stages and the infant rat brain cytosol factor stimulating the DNA synthesis in infant rat brain nuclei

[ 3H]TTP incorporation into DNA of isolated nuclei from the brains of rats at different post-partal stages, as well as the effects of the adult and the infant rat brain cytosols upon the DNA synthesis in the isolated nuclear system, have been investigated. The nuclear system requires the four deoxyribonucleoside triphosphates, ATP and Mg 2+ for a maximum activity and DNA synthesis proceeds linearly within 30 min of incubation. A large portion of [ 3H]TTP incorporated into DNA is sensitive to actinomycin D inhibition and seems to be DNA polymerase dependent, while the remaining incorporation (approx. 20 % in the infant nuclear system and approx. 40 % in the adult nuclear system) is less sensitive to actinomycin D inhibition, proceeds without dATP, dCTP and dGTP and seems to be due to the terminal DNA nucleotidyltransferase activity. The nuclear activity of [ 3H]TTP incorporation into DNA increases after birth, reaches a maximum on the fifth day and then declines rapidly, reaching the adult level ( i. e. one half the maximum level) on the 22nd day after birth. [ 3H]TTP incorporation into DNA of isolated infant rat brain nuclei is stimulated specifically by the infant rat brain cytosol. The active principle in the infant rat brain cytosol seems to be thermostable and low molecular, and differs from the stimulatory factor present in the serum.

Partial purification and characterization of spermine synthase from rat brain

Spermine synthase, the enzyme catalyzing the formation of spermine from spermidine and 5′-ndeoxy-5′- S-(3-methylthiopropylamine)sulphonium adenosine (decarboxylated S-adenosylmethionine) has been purified more than 100-fold from rat brain cytosol fraction. Spermine synthase activity can be resolved from the other polyamine-synthesizing enzyme activities, i.e. from S-adenosylmethionine decarboxylase and spermidine synthase activities, by a single chromatography run on DEAE-cellulose. The purified spermine synthase, free of any S-adenosylmethionine decarboxylase or spermidine synthase activity, showed a broad pH optimum between 7.5 and 8.1 and an acidic isoelectric point at pH 5.0. Spermine synthase appeared to have a high affinity for decarboxylated S-adenosylmethionine, the apparent K m value being below 0.005 mM. The K m for spermidine was 0.07 mM. Putrescine was shown to be a competitive inhibitor with respect to spermidine, and spermine, the product of the reaction, was also inhibitory. No metal or other cofactor requirements for spermine synthase were found.

Regional and subcellular distribution of aminotransferases in rat brain.

Abstract— Aminotransferase activity was measured in various areas of the nervous system of the rat (cortical grey matter, midbrain, corpus callosum, spinal cord and sciatic nerve) and in subcellular fractions of rat brain (nuclei, mitochondria and cytosol). Activity was low or absent in the sciatic nerve relative to that in the other areas, with the exception of incubation of glutamate with oxaloacetate (25 per cent of the activity found in brain) and of asparagine with 2‐oxoglutarate (65 per cent of the activity found in brain). The distribution of enzymic activity was not homogeneous; alanine‐2‐oxoglutarate aminotransferase was highest in cortical grey matter; leucine‐ and GABA‐2‐oxoglutarate aminotransferases were highest in midbrain. Incubation of phenylalanine or tyrosine with 2‐oxoglutarate gave similar activities in grey matter and midbrain. Activity generally was higher in the grey matter than in corpus callosum or spinal cord. However, incubations of methionine with 2‐oxoglutarate, or glutamine with glyoxylate, gave similar activities in the three areas studied from the brain, whereas incubations of glutamate with glyoxylate gave highest activity in the corpus callosum. Only incubations of asparagine with 2‐oxoglutarate, and glutamate with glyoxylate, gave significant activity in the nuclear subcellular fraction. Aminotransferase activity of phenylalanine, tyrosine or GABA with 2‐oxoglutarate, or ornithine or glutamine with glyoxylate, was localized to mitochondria. The remaining reactions studied (glutamate with oxaloacetate; leucine, alanine, methionine or asparagine with 2‐oxoglutarate and glutamate with glyoxylate) demonstrated activity in both the mitochondrial fraction and the soluble supernatant fraction.

Corticosterone-binding molecules in rat brain cytosols: regional distribution

Corticosterone-binding molecules in rat brain cytosols: regional distribution

Extracellular space of rat cerebral cortex.

Extracellular space of rat cerebral cortex.