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11.
Studies on the Tissue Distribution of the Puromycin-Sensitive Enkephalin-Degrading Aminopeptidases 总被引:3,自引:0,他引:3
Stacey McLellan Simon H. Dyer Gerry Rodriguez Louis B. Hersh 《Journal of neurochemistry》1988,51(5):1552-1559
An antiserum generated to the soluble form of the rat brain puromycin-sensitive enkephalin-degrading aminopeptidase was used to determine the tissue distribution of the soluble and membrane-associated forms of this enzyme. All tissues examined contained significant levels of the soluble enzyme form, with this enzyme accounting for greater than 90% of the arylamidase activity in brain, heart, and skeletal muscle. Native gel electrophoresis coupled with activity staining as well as inhibition studies were used to confirm the presence of this enzyme in various tissues. Serum was found not to contain this particular aminopeptidase. In contrast to the results obtained with the soluble enzyme form, brain was the only tissue found to contain the membrane-associated enzyme form. Although all tissues contained membrane-associated aminopeptidase activity only the brain enzyme could be maintained in solution in the absence of detergent. In addition, the brain membrane-associated enzyme could be distinguished from the membrane-associated aminopeptidase activity in other tissues on the basis of its sensitivity to inhibition by puromycin. 相似文献
12.
13.
Pradip Bhatnagar William Huffman Andrew King Louis Pelus William Potts et al. 《Journal of Ornithology》1994,135(1):61-71
Research Notes on Avian Biology 1994: Selected Contributions from the 21st International Ornithological CongressMorphology and Physiology: Endocrinology
Subject: Endocrinology and chronobiology 相似文献14.
15.
The small-subunit ribosomal DNA (rDNA) coding sequence was determined for the help Costaris Costata (Phaeophyta) and compared to those of chlorophyll a + b- and chlorophyll a + c-containing vascular and nonvascular plants. Phylogenetic comparison of all sequences indicated a common ancestor for phaeophytes, chrysophytes and oomycetes. Phylogenies based on rDNA sequence data and those based on plastid characteristics were compared. Relative evolutionary distances between some taxa, derived from rDNA sequence data, conflicted with findings of plastid-based phylogenies. 相似文献
16.
Culturally-transmitted feeding behaviour in primates: Evidence for accelerating learning rates 总被引:1,自引:0,他引:1
Louis Lefebvre 《Primates; journal of primatology》1995,36(2):227-239
Cultural transmission implies the rapid spread of behavioural innovations when initially naïve individuals copy more informed ones. Mathematical models of transmission feature accelerating (and in most cases, logistic) rates of learning as animals that acquire an innovation provide ever increasing numbers of informers for potential learners. Conversely, non-accelerating rates have been proposed as a null hypothesis for apparent cases of cultural transmission that can best be explained by simpler mechanisms such as trial-and-error learning. Using the AIC technique for comparing models with different numbers of parameters, this paper examines the 21 cases in the primate literature where quantifiable data are available on learning rates for presumed culturally-transmitted feeding innovations. In each case, cumulative distributions over time of the frequency or proportion of individuals that acquire an innovation are compared with three accelerating functions (logistic, positive exponential, and hyperbolic sine) and two non-accelerating ones (linear and logarithmic). In 16 cases, the best fit is given by an accelerating function: nine of these support the logistic, four support the positive exponential and three, the reverse S-shaped hyperbolic sine. Individual cases often show small differences between alternative functions, but overall trends support the cultural assumption of accelerating learning rates. 相似文献
17.
The conversion of phosphoethanolamine to phosphocholine requires 3 separate N-methyltransferases. We had previously purified the enzyme catalyzing the last methylation, phosphodimethylethanolamine N-methyltransferase. We have successfully purified the enzyme catalyzing the initial methylation of phosphoethanolamine. A 434 fold purified enzyme from rat brain was obtained by the sequential use of ammonium sulfate fractionation, Q-Sepharose fast flow column chromatography and a -aminoethyl agarose column chromatography. The pH optimum was 11 or greater, the Km value for phosphoethanolamine was 167.8±41.7 M and the Vmax was 487.3±85 mmoles/mg/hr. The kinetics for S-adenosyl-methionine, the methyldonor, has characteristics of cooperative binding with a Km of 1.805±0.59 mM and a Vmax of 16.9±3.6 moles/mg/hr. The activity was stimulated 6 fold by 2.5 mM MnCl2 and inhibited by DZA and S-adenosylhomocysteine. These results reinforce the early in vivo observations which had provided suggestive evidence for the existence of a pathway for the methylation of phosphoethanolamine to phosphocholine in rat brain.Abbreviations used Adomet
S-adenosylmethionine
- AdoHcy
S-adenosyl-homocysteine
- CAPS
3-(cyclohexyl)amino-1-propanesulphonic acid
- Cho
choline
- 3-DZA
3-deazaadenosine
- Etn
ethanolamine
- N-MT
N-methyltransferase
- PEG
polyethyleneglycol
- PMSF
phenylmethanesulphonyl fluoride
- PEtn
phosphoethanolamine
- PCho
phosphocholine
- PMe2Etn
phosphodimethylethanolamine
- PtdCho
phosphatidylcholine
- PtdEtn
phosphatidylethanolamine 相似文献
18.
Metronidazole and the isolation of temperature-sensitive photosynthetic mutants in cyanobacteria 总被引:7,自引:0,他引:7
A procedure has been developed for use of metronidazole (2-methyl-5-nitroimidazole-1-ethanol) as an enrichment agent during the isolation of temperature-sensitive, photosynthetic mutants in the cyanobacteriumSynechococcus cedrorum. The protocol includes incubation with this drug following mutagenesis withN-methyl-N-nitro-N-nitrosoguanidine. Incubation of photosynthetically activeS. cedrorum cells with 1 mM metronidazole causes a light-dependent reduction of cell viability. Maximum reduction in cell viability occurred following 6 h of incubation. Cessation of electron transport reduced the impact of the drug by five orders of magnitude. Yet during the time of incubation, metronidazole did not influence the electron transport capacities of theS. cedrorum cells, suggesting that the thylakoid membrane was not the target of the toxic effects of this drug. In addition, this drug was found to be an effective electron acceptor to photosystem I although high concentrations were required to observe maximum rates of electron transfer. Metronidazole interacted in a noncompetitive manner with methyl viologen, which suggested that those two acceptors to photosystem I have unique reduction sites on theS. cedrorum thylakoid membrane. The temperature-sensitive strains that were isolated using the procedure presented here were assessed for photosynthetic electron transport and chlorophyll fluorescence (induction kinetics and low-temperature emission spectra) characteristics. Approximately one-half of the temperature-sensitive mutants isolated possessed abnormal photosynthetic properties when shifted to the restrictive temperature (40°C). A total of 31 strains have been characterized and initially classified, showing abnormalities throughout the photosynthetic electron-transport chain. 相似文献
19.
Abstract— The effects of monovalent and divalent anions on the choline acetyltransferase reaction have been determined at high (5.0 mM) and low (0.58 mM) choline. At 0.58 mM-choline, both monovalent and divalent anions activate the enzyme ±9 fold; however, at 5.0mM-choline, monovalent anions activate the enzyme ±25 fold, while divalent anions activate ±9 fold. Both monovalent and divalent anions show uncompetitive activation with respect to choline. When either dimethylaminoethanol, N -(2-hydroxyethyl)- N -methyl piperidinium iodide, or N -(2-hydroxyethyl)- N -propyl pyrrolidinium iodide was substituted for choline, activation by monovalent or divalent anions was only 2.5-4 fold. With AcCoA as substrate the ChA reaction can be increased ±20 fold by increased salts; however, with acetyl dephosphoCoA as substrate, the reaction is insensitive to the salt concentration. Similar salt effects on the ChA reaction, as measured in the direction of acetylcholine synthesis, have been demonstrated in the reverse reaction. In addition, inhibition of the forward reaction by acetylcholine has been measured as a function of sodium chloride concentration. Although the K1 for acetylcholine increases with increasing salt, this change in K 1 , parallels the increase in the K m for choline. These results support the hypothesis that both monovalent and divalent anions activate choline acetyltransferase by the same singular mechanism; which is to increase the rate of dissociation of coenzyme A from the enzyme. 相似文献
20.