摘要:

Abstract—1L‐Alanine: α‐oxoglutarate aminotransferase was partly purified from rat brain and liver. The enzyme from the brain has about 10 times less activity than that from the liver.2Both enzymes have identical apparentKmvalues for L‐alanine, L‐glutamate, α‐oxoglutarate and pyruvate. Moreover they are competitively inhibited by L‐leucine. α‐oxoisocaproate and α‐oxotsovalerate. Obtained K, values are very similar and do not depend on the course of reaction.3α‐Oxoisocaproate inhibits the activity of crystalline L‐aspartate: α‐oxoglutarate aminotransferase;Kjis about 4–7 mM.4The pyridoxamine form of L‐alanine: α‐oxoglutarate aminotransferase seems to be more sensitive to the inhibitory effect of the compounds investigated.5The effect of branched‐chain amino acids and their α‐oxoanalogues on the metabolism of amino groups

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1974.tb12181.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—1Among 16 amino acids tested only D‐ and L‐glutamate were found to be specific inhibitors of citrate lyase from adult rat brain. Glutamate also inhibited citrate lyase from the liver of starved animals while it was without effect on lyase from those refed with carbohydrate. L‐Glutamate did not inhibit the citrate lyase from brains of newborn rats.2The inhibitory effect of L‐glutamate was increased when the time of preincubation was prolonged, but only in the presence of both ATP and MgCl2. This time‐dependent inhibition could be reversed by addition of high concentrations of ATP.3L‐Glutamate was without effect onKmandVmaxvalues for MgCl2. Excess of Mg2+ions was indispensable for glutamate inhibition.4L‐Glutamate was shown to be competitive with respect to the ATP inhibitor of the lyase, with a Kiof 0.3mM.5The mechanism of L‐glutamate inhibition may be due to the reaction of a glutamate‐Mg complex with the phosphorylated intermediary form of the lyase, resulting in the formation of a lyase‐glutamate complex.6The physiological significance of the inhibitory action of g

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1974.tb12182.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—High phosphodiesterase activity for cyclic AMP and cyclic GMP was found in subcellular fractions of the bovine retina with more rapid hydrolysis of cyclic GMP than cyclic AMP in each fraction. Rod outer segments (ROS) and the supernatant fraction had highest activity. High enzyme activity remained associated with ROS membranes through several steps of purification by gradient centrifugation. A complex kinetic pattern was observed for cyclic AMP hydrolysis by the supernatant fraction yielding two values forKm; a simple kinetic pattern was observed with cyclic GMP hydrolysis in supernatant and for both cyclic nucleotides in preparations of purified outer segments. Phosphodiesterase activity of outer segments was enhanced by Mg2+. Mn2+and inhibited by EDTA. Cyclic AMP had relatively little effect on the hydrolysis of cyclic GMP in supernatant or ROS while cyclic GMP inhibited hydrolysis of cyclic AMP in both fraction

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1974.tb12183.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—High affinity uptake systems for GABA into slices of cerebral cortex and for glycine into slices of spinal cord have been demonstrated in rats of 1 and 10 days postnatal age and compared with the systems in tissue slices from adult rats. For both systems there was an increase in the maximal rate of uptake of the substrate with development. For glycine uptake there was no significant change in apparentKmduring development, whereas there was a four‐fold increase in the apparentKmfor GABA uptake. There were some changes with development in the apparent substrate specificity of the two systems suggesting increased specificity with maturation. Bicuculline and strychnine, antagonists of the postsynaptic inhibitory actions of GABA and glycine, produced convulsions in 1‐, 2‐ and 10‐day‐old rats following intraperitoneal injection of doses somewhat lower than those required to convulse adult rats. These findings are consistent with other evidence that glycine and GABA are functioning as inhibitory transmitters at least as soon as 1 day

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1974.tb12184.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—Of the amino acids found in the CNS of 10‐day‐old rats the concentration of glycine alone was significantly higher in the spinal cord than in all other regions. Spinal levels of glycine, cystathionine, isoleucine and lysine from 1‐ and 10‐day‐old rats did not differ significantly from adult values, whereas the levels of most other amino acids, including GABA, glutamate, glutamine and taurine, were higher in the young animals than in the adults. Aspartate was the only amino acid found in lower concentration in the spinal cord of young animals than in adult animals. These and other observations support the conclusion that glycine is used as an inhibitory transmitter in rat spinal cord early in postnatal life. There was a general decrease in the activity of serine hydroxymethyltransferase and a slight increase in the activity of glycine:2‐oxoglutarate aminotransferase in the CNS during development. The activity of neither enzyme correlated on a regional basis with the glycine content. The high level of hydroxymethyltransferase activity in the cerebellum of 10‐day‐old rats suggests that the activity of this enzyme reflects

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1974.tb12185.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—The activity of DNA‐dependent RNA polymerase and the synthesis of microsomal protein were investigated after various periods of anoxic condition produced with rabbit brain in anin vitroexperimental model. There was prompt inhibition of protein synthesis even after an anoxic period of 5 min, and inhibition was more than 80 per cent after an anoxic period of 30 min. However, RNA polymerase activity was retained during the early stage of anoxia, but definite inhibition appeared after an anoxic period of 15 min. Comparisons with other available information suggest that the inhibition of protein synthesis observed with brain slices is closely related to their polysomal function, that irreversibility of inhibition of protein synthesis might be related to the involvement of nuclear RNA synthesizing mechanism, and that these can occur both in the neuronal and glial eleme

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1974.tb12186.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—An analysis of proteins undergoing axonal transport in nigro‐striatal neurons, after the stereotaxic injection of [3H]leucine into the substantia nigra of rat brain was performed. As early as 6 h after the injection [3H]proteins appeared in the caudate‐putamen. The maximum accumulation was at 5 days and there was still residual protein radioactivity present at 30 days. About 70 per cent of the total radioactive protein in the caudate‐putamen was solubilized by homogenization in 0–5%, (v/v) Triton X‐100 and remained in the supernatant on centrifuging for 1 h at 100,000g.The supernatant fraction, when chroma‐tographed on a DEAE‐cellulose column, was resolved into four protein peaks (A, B. C and D) which were found to be labelled differently as a function of time after the injection of [3H]leucine. Peak A was substantially labelled in a first phase (6–24 h) and reached its maximum in a second phase (5 days). The proteins comprising this peak appeared to undergo both fast and slow axonal transport. Although some labelling in peak B was evident at 6 h, maximal activity did not occur until 5 days. No radioactivity could be detected in peaks C and D at 6 h. Maximal labelling of these two peaks also occurred at 5 days. These data suggest that the proteins of peaks B, C and D were transported primarily by slow axoplasmic flow. The radioactive protein peaks A and B from the second phase of the transport were excluded from a Sephadex G‐200 column, pointing to their high molecular weights (13,000–200,000). Peak B. which had the highest specific radioactivity (c.p.m./mg protein) at 5 days, contained a significant level of tyrosine hydroxylase, an important component of

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1974.tb12187.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—The dialysableglycopeptide preparation recovered from the glycoproteins in cerebral gray matter of a case of the O‐variant form of GM2gangliosidosis contained four fold moreN‐acetylglucosamine and mannose than a similar preparation from normal gray matter. In the O‐variant form of GM2gangliosidosis, the enzymesβ‐N‐acetylhexosaminidases A and B are missing. A three‐ and four‐fold elevation, respectively, ofN‐acetylglucosamine and mannose in the dialysable glycopeptide preparation from a case of Tay‐Sachs disease (B‐variant form of GM2gangliosidosis) was noted. The B‐variant lacks hexosaminidase A but has ample supplies of hexosaminidase B. The brain level of glycosaminoglycans was not affected in the O‐ and B‐varian

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1974.tb12188.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—A fluorimetric assay has been used to examine some kinetic properties of AChE from synaptosomal plasma membranes prepared from rat brain. The AChE bound to the plasma membranes was compared to that solubilized with Triton X‐100 and found to be essentially the same with respect to Michaelis constant and inhibitor constants for several AChE inhibitors. The two forms of the enzyme had slightly different pH optima. The kinetic studies revealed no evidence that synaptosomal plasma membrane AChE has allosteric properties. The solubilized enzyme was further purified by affinity chromatogra

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1974.tb12189.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—The thermodynamic stabilities of the coordinate binding of Cu2+ion with adenosinetriphos‐phate (ATP) and several biogenic amines have been determined in aqueous model systems in an attempt to examine the possible correlation between metal‐amine binding and thein vivoaffinities of the amines for granule‐binding. In each of the ternary chelate systems consisting of Cu2+‐ATP‐amine (1:1:1), the Cu2+ion is preferentially bound by ATP in the pH range 3–5 with a stability constant of Log KML= 517. In the pH range 5–8 each of the biogenic amines coordinates with Cu2+‐ATP chelate to form the respective ternary chelate. The nature and strength of binding of fourteen different amines with Cu2+‐ATP have been evaluated on the basis of the stabilities of the ternary chelates. On the basis of the quantitative equilibrium data generated in this study, it appears that both pyrocatechol moiety and the ethanolamine side‐chain of the catechol amines are involved in the coordination of copper. The metal‐binding stabilities of the biogenic amines are then correlated with the molecular structure, donor basicities and thein vivoaffinities of the amines for granule‐binding in order to rationalize the possible involvement of metal chelates in the monoamine bindi

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1974.tb12190.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY