Phosphatidate Phosphohydrolase in Plants and Microorganisms
David N. Brindley, John R. Sabine in Phosphatidate Phosphohydrolase, 2017
The molecular species of the chloroplastic lipids, phosphatidylglycerol and sulfoquinovosyldiacylglycerol, which are formed in labeling studies also resemble those of the accumulated diacylglycerol in isolated chloroplasts.46 These results again emphasize the pivotal role of phosphatidic acid metabolism not only in determining the overall proportions of different lipid classes but also in influencing exact molecular species distributions. Although earlier interpretation of data proposed that cytoplasmic phosphatidic acid was used for CDP-diacylglycerol formation and phosphatidylglycerol synthesis13 recent studies have demonstrated that plastids can make the latter phospholipid. Indeed, both CDP-diacylglycerol and phosphatidylglycerol synthesis are found on the envelope membranes where phosphatidic acid formation takes place.25 Thus, it is clear that the phosphatidate phosphohydrolase of chloroplasts has to compete with the CTP:phosphatidic acid cytidylyltransferase for available phosphatidate substrate. In that connection it is noteworthy that the cytidylyltransferase is severely inhibited by Triton X-10025 and, therefore, the increase in diacylglycerol labeling in intact chloroplasts with this detergent13 could have been due to the inhibition of competitive side reactions for phosphatidate phosphohydrolase.
General Introduction
David N. Brindley, John R. Sabine in Phosphatidate Phosphohydrolase, 2017
The phosphohydrolase from brain can hydrolyze monoalkylphosphate in addition to phosphatidate but it was reported not to hydrolyze dialkylphosphates or synthetic dipalmitoylphosphatidate.66 The reason for the lack of effect on the latter compound is unexpected and it may have resulted from a problem in the physical presentation of the substrate. Hexadecylphosphate was also found to be a substrate for a partially purified phosphatidate phosphohydrolase from rat liver51 and l-O-hexadecyl-rac-[2-3H]glycerol 3-phosphate is hydrolyzed by human amniotic fluid.46 A preparation from erythrocytes was able to hydrolyze 1,3-diacylglycerol 2-phosphate.67 It has also been suggested that phosphatidylglycerol phosphate is a substrate for phosphatidate phosphohydrolase and this will be discussed in greater detail in Chapter 5, Sections XIII and XVII.
Amniocentesis
Hung N. Winn, Frank A. Chervenak, Roberto Romero in Clinical Maternal-Fetal Medicine Online, 2021
Fetal lung maturity can be assessed indirectly using both qualitative and quantitative characteristics of amniotic fluid. Pulmonary maturity can be assessed by the measurement of lecithin/sphingomyelin ratio or the concentration of phosphatidylglycerol in amniotic fluid. Similarly, the detection of lamellar bodies and the study of other characteristics of the amniotic fluid may give information about lung maturity. However, the improvement in neonatal care and the accurate confirmation of gestational age with ultrasound early in pregnancy have diminished the need for examination of amniotic fluid and thus amniocentesis in order to confirm lung maturity.
Factors determining phage stability/activity: challenges in practical phage application
Published in Expert Review of Anti-infective Therapy, 2019
Ewa Jończyk-Matysiak, Norbert Łodej, Dominika Kula, Barbara Owczarek, Filip Orwat, Ryszard Międzybrodzki, Joanna Neuberg, Natalia Bagińska, Beata Weber-Dąbrowska, Andrzej Górski
In a study by Nobrega et al. (2016), a T7 E. coli phage was used as a model and its genome was modified with the E. coli phosphoporin E protein peptide signal (PhoE) by linking it to the major capsid protein, allowing phospholipids to attach to the phage capsid [186]. During transcription, the assembled phage mutant was able to bind phospholipids from the internal leaflet of the cytoplasmic membrane after ionic interaction with the polar head group, e.g. phosphatidylglycerol. The stability of the recombinant phages was tested under simulated GIT conditions. The results showed better stability of mutant phages compared to wild-type phages (e.g. phage incubation in gastric juice caused significant loss in the titer of T7 phage (wild type) after 90 and 120 min, whereas the T7 PhoE mutant retained its titer without any significant changes). This work presents an alternative to encapsulation, based on the use of phage-engineering methods, which may be a promising strategy to provide additional phage protection against the acidic environment and hostile conditions present in the GIT.
Investigations of the influence of liposome composition on vesicle stability and drug transfer in human plasma: a transfer study
Published in Journal of Liposome Research, 2018
Stephan Holzschuh, Kathrin Kaeß, Guilherme Volpe Bossa, Christiane Decker, Alfred Fahr, Sylvio May
For each composition of phosphatidylcholine and phosphatidylglycerol, k1, k2 and k3 were calculated by minimizing the cumulative difference square between the theoretical curves (Equations. (6–9)) and the values measured experimentally. With these constants established, we used the same minimization procedure to determine the initial amounts, Mi(0) and Mo(0) for each specific formulation. The results are displayed in Table 2. With k4 = k5 =0 all drug will eventually be transferred to either HDL or LDL. However, our experimental data typically reveal a plateau at long incubation times, with some drug remaining in the liposomes. To account for the plateau, we also consider an extension of our model where k4 and k5 are non-vanishing. We refer to this extended model as 5k-model. Figure 8 shows two exemplary fits for a DPPC/DPPG formulation containing 8 mol% mTHPC (Foslip®) and the PEGylated Fospeg®. Solid and dashed curves correspond to the 3k and 5k models, respectively. The fit of our 3k and 5k models reveals reasonable agreement with the experimentally observed trends. This, in fact, is a characteristic feature for all data sets that we have modeled. While the 5k model necessarily yields better agreement, it also contains two more fitting parameters. In contrast, the 3k-model preserves all the physically relevant features with only 3 rate constants. We thus argue that the 3k-model represents the more robust modeling approach. Consequently, our following discussion focuses on the 3k-model.
Ultrastructural analysis of the intracellular surfactant in lungs of healthy and ovalbumin sensitized and challenged Brown Norway rats
Published in Experimental Lung Research, 2023
Andreas Schmiedl, Stefanie Frank, Thomas Tschernig, Jens M. Hohlfeld
Alterations in the composition of phospholipids, which are not visible microscopically, may also influence the intra-alveolar surfactant activity. e.g., a diminution in phosphatidylglycerol (PG) correlated with increased surface tension combined with an increase of inactive surfactant components.33 Furthermore, it was suggested that the loss of PG by, for instance. increased phospholipase activity, may contribute more to surfactant dysfunction than alterations of surfactant proteins, loss of posphatidylcholine or increased levels of lysophospholipids, or the presence of increased numbers of eosinophils.61 In asthmatic animals compared to controls, decreased surfactant pool sizes and saturated phosphatidylcholine to protein ratios in BALF may predominantly be induced by leaked serum proteins.32 Summarizing the results of other authors, asthma induced inflammation predominantly disturbs the intra-alveolar surfactant pool in different ways.
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