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1.
2.
Channeling of ammonia from glutaminase to carbamoyl-phosphate synthetase in liver mitochondria 总被引:2,自引:0,他引:2
A J Meijer 《FEBS letters》1985,191(2):249-251
In isolated rat-liver mitochondria the rate of citrulline synthesis from glutamine does not respond to changes in the ammonia concentration in the extramitochondrial fluid. This suggest that ammonia, produced in the mitochondria via glutaminase, is directly channeled to carbamoyl-phosphate synthetase. 相似文献
3.
Ronald J.A. Wanders Carlo Van Roermund Cor Lof Alfred J. Meijer 《Analytical biochemistry》1983,129(1):80-87
A simple fluorimetric assay for the determination of carbamoyl phosphate in tissue extracts is described. In the assay, production of ATP from carbamoyl phosphate and ADP by carbamate kinase is coupled to the formation of NADPH, using glucose, hexokinase, NADP+, and glucose-6-phosphate dehydrogenase. Production of NADPH in this system proved to be equal to the amount of carbamoyl phosphate present. 相似文献
4.
A Merlin W Voos A C Maarse M Meijer N Pfanner J Rassow 《The Journal of cell biology》1999,145(5):961-972
Tim44 is a protein of the mitochondrial inner membrane and serves as an adaptor protein for mtHsp70 that drives the import of preproteins in an ATP-dependent manner. In this study we have modified the interaction of Tim44 with mtHsp70 and characterized the consequences for protein translocation. By deletion of an 18-residue segment of Tim44 with limited similarity to J-proteins, the binding of Tim44 to mtHsp70 was weakened. We found that in the yeast Saccharomyces cerevisiae the deletion of this segment is lethal. To investigate the role of the 18-residue segment, we expressed Tim44Delta18 in addition to the endogenous wild-type Tim44. Tim44Delta18 is correctly targeted to mitochondria and assembles in the inner membrane import site. The coexpression of Tim44Delta18 together with wild-type Tim44, however, does not stimulate protein import, but reduces its efficiency. In particular, the promotion of unfolding of preproteins during translocation is inhibited. mtHsp70 is still able to bind to Tim44Delta18 in an ATP-regulated manner, but the efficiency of interaction is reduced. These results suggest that the J-related segment of Tim44 is needed for productive interaction with mtHsp70. The efficient cooperation of mtHsp70 with Tim44 facilitates the translocation of loosely folded preproteins and plays a crucial role in the import of preproteins which contain a tightly folded domain. 相似文献
5.
The rate of proteolysis is an important determinant of the intracellular protein content. Part of the degradation of intracellular
proteins occurs in the lysosomes and is mediated by macroautophagy. In liver, macroautophagy is very active and almost completely
accounts for starvation-induced proteolysis. Factors inhibiting this process include amino acids, cell swelling and insulin.
In the mechanisms controlling macroautophagy, protein phosphorylation plays an important role. Activation of a signal transduction
pathway, ultimately leading to phosphorylation of ribosomal protein S6, accompanies inhibition of macroautophagy. Components
of this pathway may include a heterotrimeric Gi3-protein, phosphatidylinositol 3- kinase and p70S6 kinase. Recent evidence
indicates that lysosomal protein degradation can be selective and occurs via ubiquitin- dependent and -independent pathways.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
6.
7.
Summary Nitrification of ammonia in concentrated waste streams is gaining a lot of attention nowadays. Nitrosomonas europaea is the predominant ammonia-oxidizing species in these environments. Prediction of the behaviour of a pure culture of N. europaea (ATCC 19718) under conditions prevailing in concentrated waste streams was the aim of this study. The initial oxygen consumption rate of a concentrated cell suspension was used as a rapid assay to measure the effects on N. europaea under various conditions. Several relationships, based on Michaelis-Menten kinetics, were derived. They describe the behaviour of N. europaea at substrate (NH4
+), product (NO2
– and K+, Na+, SO
inf4
sup2–
, NO3
–, Cl–) concentrations up to 500 mol/m3 and pHs ranging from 6.5 to 8.5. High concentrations of ions inhibited N. europaea but specific substrate inhibition was not observed. Product inhibition was strongly pH-dependent and severe inhibition was found at pH 6.5.
Correspondence to: J. H. Hunik 相似文献
8.
H. J. P. M. Koenen Marjon J. Smit Marleen M. J. A. Simmelink Bart Schuurman Robert H. J. Beelen Sybren Meijer 《Cancer immunology, immunotherapy : CII》1996,42(5):310-316
Milky spots in the greater omentum are small accumulations of leucocytes that consist mainly of macrophages and have recently
shown to be a selective dissemination site of intraperitoneal (i. p.) inoculated tumour cells. However, milky-spot macrophages
show tumoricidal activity and may, therefore, be an excellent source of effector cells suited for local immunotherapy. In
the present study we first examined whether granulocyte/macrophage- colony-stimulating factor (GM-CSF) treatment of isolated
milky-spot macrophages affects the cytotoxicity against syngeneic colon carcinoma cells (CC531) in vitro. Secondly, we studied
the influence of intraperitoneal GM-CSF administration on the number and antitumour activity of milky-spot and peritoneal
macrophages. All studies were performed in Wag/Rij rats in which a syngeneic colon carcinoma cell line (CC531) is available.
The results of the in vitro study showed that GM-CSF treatment of the omental macrophages led to an increased cytotoxicity
against the tumour cell line. Intraperitoneal administration of 1000 U GM-CSF daily for 7 consecutive days demonstrated both
an enhanced antitumour activity of the milky-spot macrophages and an increase in the milky-spot macrophage population. An
increase in the proliferative capacity, according to bromodeoxyuridine incorporation, was shown in the milky-spot macrophages.
Taking into account both the enhanced macrophage number and their enhanced activity upon i. p. GM-CSF treatment, the milky-spot
macrophages may provide a rationale for local intraperitoneal immunotherapy in the prevention of intra-abdominal tumour growth.
Received: 11 April 1996 / Accepted: 21 May 1996 相似文献
9.
In the present study we show that the enzymatic activity of the coenzyme nicotinamide adenine dinucleotide (NAD+) and its analogues (C(O)NH2 replaced by C(S)NH2, C(O)CH3, C(O)H and CN) with horse liver alcohol dehydrogenase (LADH) (alcohol:NAD+ oxidoreductase, EC 1.1.1.1) can be rationalized by their conformation in the active site determined with molecular mechanics (AMBER, assisted model building with energy refinement). In order to establish the relation between the hydride transfer rate and the conformation of the NAD+ and its analogues, kinetic experiments with the poor substrate isopropanol were carried out. It appears that the enzymatic activity can be readily explained by the geometry of the pyridinium ring, in particular the magnitude of the 'out-of-plane' rotation of the carboxamide side chain (or analogues). The latter is nicely illustrated in the case of 3-cyanopyridine adenine dinucleotide which lacks any 'out-of-plane' rotation and concomitantly exhibits no significant enzymatic activity. 相似文献
10.
Frank J. J. Segers Martin Meijer Jos Houbraken Robert A. Samson Han A. B. W?sten Jan Dijksterhuis 《PloS one》2015,10(12)
Indoor fungi are a major cause of cosmetic and structural damage of buildings worldwide and prolonged exposure of these fungi poses a health risk. Aspergillus, Penicillium and Cladosporium species are the most predominant fungi in indoor environments. Cladosporium species predominate under ambient conditions. A total of 123 Cladosporium isolates originating from indoor air and indoor surfaces of archives, industrial factories, laboratories, and other buildings from four continents were identified by sequencing the internal transcribed spacer (ITS), and a part of the translation elongation factor 1α gene (TEF) and actin gene (ACT). Species from the Cladosporium sphaerospermum species complex were most predominant representing 44.7% of all isolates, while the Cladosporium cladosporioides and Cladosporium herbarum species complexes represented 33.3% and 22.0%, respectively. The contribution of the C. sphaerospermum species complex was 23.1% and 58.2% in the indoor air and isolates from indoor surfaces, respectively. Isolates from this species complex showed growth at lower water activity (≥ 0.82) when compared to species from the C. cladosporioides and C. herbarum species complexes (≥ 0.85). Together, these data indicate that xerotolerance provide the C. sphaerospermum species complex advantage in colonizing indoor surfaces. As a consequence, C. sphaerospermum are proposed to be the most predominant fungus at these locations under ambient conditions. Findings are discussed in relation to the specificity of allergy test, as the current species of Cladosporium used to develop these tests are not the predominant indoor species. 相似文献