Phosphorylation preferential

Aciclovir is phosphorylated preferentially by herpes simplex virus-coded thymidine kinase and following further phosphorylation aciclovir triphosphate interferes with herpes virus DNA polymerase and viral DNA replication. Aciclovir topical cream is indicated in the management of initial genital herpes and in limited non-life threatening mucocutaneous herpes simplex virus infections in immunocompromised patients. 

Finally, a group of phenoxytriethylamines, originally synthesized as potential uncouplers of oxidative phosphorylation, preferentially inhibit lycopene cyclization. ... 

Cellular phosphoinositide concentrations are under tight control by phospholipid kinases and phosphatases. Phospholipid kinases preferentially phosphorylate distinct positions of the inositol ring and hence are subdivided into phosphoinositide 3-kinases (PI3Ks), phosphoinositide 4-kinases (Pl4Ks), and phosphoinositide 5-kinases (PI5Ks) that phosphorylate Pis on position 3, 4 and 5, respectively. In a canonical pathway, Ptdlns... 

When 14-3-3s were first identified as phosphorylation dependent binding proteins (note that a selection of non-phosphorylated targets are known), target protein phosphorylation sites were mapped and it was immediately apparent that 14-3-3s bound preferentially to specific phosphorylation motifs. The advent of oriented... 

The condensation reactions are preferentially carried out in pyridine. As reactive species for phosphorylation of the nucleoside R OH (synthesis of a phosphortriester), the phosphoric acid azolide has been assumed. The mixed phosphoric sulfonic anhydride and a pyrophosphate tetraester have been suggested as intermediates leading to the phosphoric acid azolide. 

Marine algae transform arsenate into nonvolatile methylated arsenic compounds such as methanearsonic and dimethylarsinic acids (Tamaki and Frankenberger 1992). Freshwater algae and macrophytes, like marine algae, synthesize lipid-soluble arsenic compounds and do not produce volatile methylarsines. Terrestrial plants preferentially accumulate arsenate over arsenite by a factor of about 4. Phosphate inhibits arsenate uptake by plants, but not the reverse. The mode of toxicity of arsenate in plants is to partially block protein synthesis and interfere with protein phosphorylation — a process that is prevented by phosphate (Tamaki and Frankenberger 1992). 

In order to synthesize biologically relevant phosphonylimidazole 73, bromoimidazole 72 was derived from radical-initiated bromination of methyl l-p-methoxybenzyl-2-thiomethyl-5-imidazolylcarboxylate (71) [56]. The thiomethyl group served to block the C(2) position, which would otherwise undergo preferential halogenation under these conditions. As expected, a variety of Arbusov-Michaelis reaction conditions failed even under forcing conditions. On the other hand, Pd-catalyzed phosphorylation of 72 with diethyl phosphite led to methyl-4-diethylphosphonyl-l-p-methoxybenzyl-2-thiomethyl-5-imidazolylcarboxylate (73). After further manipulations, the desired phosphonic acid-linked aminoimidazoles, which resembled intermediates formed during purine biosynthesis, were accessed. 

The regiospecificity of the exclusive O-acylation [8] and O-phosphorylation [9] of P-dicarbonyl compounds (Chapter 3) also illustrates the effect of phase-transfer catalysts on the stereochemical course of reactions. Similarly, directed reduction of P-hydroxy ketones using tetramethylammonium trisacetoxyborohydride leads to the preferential formation of the anti dihydroxy system in high yield with a stereoselectivity >95% [10] (Section 11.4). 

The majority of PC is synthesized in mammalian cells by the CDP-choline or Kennedy pathway in the endoplasmic reticulum (Eigiue 1). In this pathway, choline taken up from the external medium or released in the cytosol by breakdown of choline containing compoimds, is first converted to phosphocholine by the enzyme choline kinase (CK) (Ishidate, 1997). There are two isoforms of CK cloned which both can convert also ethanolamine to phosphoethanolamine, albeit with a lesser affinity (Aoyama et al 2000). Alternatively phosphocholine can be generated by enzymes that preferentially phosphorylate ethanolamine and are therefore designated ethanolamine kinases (EK). As yet also two different EKs are known (EKI 1 and 2 Lykidis etal., 2001). 

ET), which catalyzes the formation of CDP-ethanolamine, and (iii) an ethanolaminephosphotransferase (EPT), which finally synthesizes PE from DAG and CDP-ethanolamine. As discussed rmder PC synthesis, four enzymes have been cloned that can phosphorylate ethanolamine, two of which preferentially use ethanolamine as a substrate, and two which are more specific for choline. Only one isoform of ET has been cloned, which contains two active sites, but seems to be not as strictly regulated compared to its counterpart CT (Bladergroen et al, 1999a). 

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