Phospholipid synthesizing

The lipids in the viral envelope are taken from the host cell. Pfef-ferkorn and Hunter (1963) had already shown that the viral phospholipids are largely derived from cellular phospholipids synthesized before infection. Subsequent studies of the phospholipid, glycolipid, and cholesterol content of the alphaviruses have shown that the lipid composi-... 

During phagocytosis, new phospholipids synthesized from triglyceride may be utilized to form the membrane of the phagocytic vesicles (S8). 

Baking and brewing, food processing, production of natural sweeteners, use in transesterification and oligosaccharide, peptide, and phospholipid syntheses... 

Enzymological studies on phospholipid-synthesizing enzymes in plants have turned up no m or differences from analogous enzymes in animals and microorganisms. The subcellular location of the enzymes in mitochondria and the ER is also similar to the situation in animal tissue. The enzymes associated with the chloroplast are of particular interest, both in the synthesis of LPA and PA. Further studies on the chloroplast should reveal important aspects of the phospholipid economy, such as the origin of the phospholipids of the chloroplast envelope and the origin of PG in the lamellae. 

Even though recent work has provided useful information about the sub-cellular location of phospholipid-synthesizing enzymes, more detailed resolution and assay of membranes are now called for. We need to know the relative biosnythetic abilities of smooth and rough ER, the plasma membrane, and the tonoplast. 

The environment for the phospholipid synthesizing enzymes plays a major role In their activity. By environment I refer to pH, Ion, and membrane lipid requirements. I previously have discussed the pH and Ion requirements. In particular the dichotomy of requirements for magnesium and manganese by the DAG and CDP-DAG pathways of phospholipid synthesis Calcium plays a role In exchange reactionsand has been described as... 

As will be described later, the kinetics of appearance of enzymes in vitro correspond well to the kinetics in vivo (Fig. 2). Together with other methods, in vivo kinetics helped to map various other genes in the left-side section of T7 DNA the genes for the translational-repressor, for the RNA shut-off function, the protein phosphokinase and a phospholipid synthesizing activity (Schweiger et al., 1972 Herrlich et al., 1973 and 1974 Rahmsdorf et al., 1973 and 1974). 

Since in vitro protein synthesis is very sensitive to ionic strength and magnesium concentrations (see Chapter II), it is reasonable to assume that this is also relevant for the synthesis of proteins in vivo. In fact we have recently observed that during TZ infection changes occur in the cellular envelope (Herrlich et al., 1973). The phospholipid pattern is different from that of uninfected cells and TZ even induces a phospholipid synthesizing activity detectable in cell extracts, which incorporates from y-labeled ATP into phosphatidic acid, phosphatidylethanolamine and phosphatidylglycerol. 

In eukaryotic cells, the enzymes responsible for the synthesis of the major phospholipids, occur in the endoplasmic reticulum. Mitochondria, however, can synthesize phosphatidic acid and cardiolipin, a phospholipid present exclusively in mitochondria (Chapter 4). In bacteria, almost all the phospholipid-synthesizing enzymes are localized in the plasma membrane. ... 

Mammals synthesize phosphatidylserine (PS) in a calcium ion-dependent reaction involving aminoalcohol exchange (Figure 25.21). The enzyme catalyzing this reaction is associated with the endoplasmic reticulum and will accept phosphatidylethanolamine (PE) and other phospholipid substrates. A mitochondrial PS decarboxylase can subsequently convert PS to PE. No other pathway converting serine to ethanolamine has been found. 

There are three groups of eicosanoids that are synthesized from C20 eicosanoic acids derived from the essential fatty acids linoleate and a-linolenate, or directly from dietary arachidonate and eicosapentaenoate (Figure 23-5). Arachidonate, usually derived from the 2 position of phospholipids in the plasma membrane by the action of phospholipase Aj (Figure 24-6)—but also from the diet—is the substrate for the synthesis of the PG2, 1X2 series (prostanoids) by the cyclooxygenase pathway, or the LT4 and LX4 series by the lipoxygenase pathway, with the two pathways competing for the arachidonate substrate (Figure 23-5). 

Triacylglycerols and some phosphoglycerols are synthesized by progressive acylation of glycerol 3-phosphate. The pathway bifurcates at phosphatidate, forming inositol phospholipids and cardiolipin on the one hand and triacylglycerol and choline and ethanolamine phospholipids on the other. 

Fat absorbed from the diet and lipids synthesized by the liver and adipose tissue must be transported between the various tissues and organs for utilization and storage. Since lipids are insoluble in water, the problem of how to transport them in the aqueous blood plasma is solved by associating nonpolar lipids (triacylglycerol and cholesteryl esters) with amphipathic hpids (phospholipids and cholesterol) and proteins to make water-miscible hpoproteins. 

In this in vitro system, the presence of serum in cell culture medium is not necessary, but the type of transwell is important (the total amount of H-triglycerides secreted was two-fold higher when using 3 pm versus 1 pm pore size transwells), and oleic acid supplementation is required for the formation and secretion of CMs as well as the transport of 3-carotene through Caco-2 cells. Finally, the presence of Tween 40 does not affect CM synthesis and secretion in this in vitro cell culture system. Thus, CMs secreted by Caco-2 cells were characterized as particles rich in newly synthesized H-triglycerides (90% of total secreted) containing apolipoprotein B (30% of total secreted) and H-phospholipids (20% of total secreted) and with an average diameter of 60 nm. These characteristics are close to those of CMs secreted in vivo by enterocytes. ... 

This book is written for the practicing pharmaceutical scientist involved in absorption-distribution-metabolism-excretion (ADME) measurements who needs to communicate with medicinal chemists persuasively, so that newly synthesized molecules will be more drug-like. ADME is all about a day in the life of a drug molecule (absorption, distribution, metabolism, and excretion). Specifically, this book attempts to describe the state of the art in measurement of ionization constants (p Ka), oil-water partition coefficients (log PI log D), solubility, and permeability (artificial phospholipid membrane barriers). Permeability is covered in considerable detail, based on a newly developed methodology known as parallel artificial membrane permeability assay (PAMPA). 

Scheme 3.5, and carotenoids have been previously incorporated into vesicles of phospholipids, Figure 3.1 (Milon et al. 1986, Britton 1998). It was therefore reasonable to connect carotenoids with a phosphate group, above all because hydrophobic phosphate esters had previously been synthesized (Sliwka 1997). The C30-monoglyceride, 3.12, was therefore used as an educt for the synthesis of the zwitterionic, hydrophobic C30-lysophosphocholine, 3.15, via aminolyse of the bromo phosphoester,... 

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