Choline sulfate

A number of enzymes known as sulfuric ester hydrolases (EC 3.1.6) are able to hydrolyze sulfuric acid esters. They comprise arylsulfatase (sulfatase, EC 3.1.6.1), steryl-sulfatase (steroid sulfatase, steryl-sulfate sulfohydrolase, arylsulfatase C, EC 3.1.6.2), choline-sulfatase (choline-sulfate sulfohydrolase, EC 3.1.6.6), and monomethyl-sulfatase (EC 3.1.6.16). Whereas mono-methyl-sulfatase is highly specific and does not act on higher homologues, arylsulfatase has a broad substrate specificity and is of particular significance in the hydrolysis of sulfate conjugates of phenols, be they endogenous compounds, drugs, or their metabolites [167-169],... 

This enzyme [EC 3.1.6.6] catalyzes the hydrolysis of choline sulfate to produce choline and sulfate. 

This enzyme [EC 2.8.2.6] catalyzes the reaction of 3 -phosphoadenylylsulfate with choline to produce adenosine 3, 5 -bisphosphate and choline sulfate. 

While esters of sulfuric acid do not play as central a role in metabolism as do phosphate esters, they occur widely. Both oxygen esters (R-0-S03 , often referred to as O-sulfates) and derivatives of sulfamic acid (R-NH-SOg, N-suIfates) are found, the latter occurring in mucopolysaccharides such as heparin. Sulfate esters of mucopolysaccharides and of steroids are ubiquitous and sulfation is the most abundant known modification of tyrosine side chains. Choline sulfate and ascorbic acid 2-sulfate are also found in cells. Sulfate esters of phenols and many other organic sulfates are present in urine. 

Among the variety of sulfate esters formed by living cells are the sulfate esters of phenolic and steroid compounds excreted by animals, sulfate polysaccharides, and simple esters, such as choline sulfate. The key intermediate in the formation of all of these compounds lias been shown to be 3 -phosphoadenosine-5/-phosphosulfate (PAPS). This nucleotide also serves as an intermediate in sulfate reduction. 

Under these conditions, a typical measured proton flux might be in the range of 10 15 mol/(cm2 s). To compare this value with that of potassium, 1 M potassium ion (as potassium sulfate) could be trapped inside the same liposomes, and potassium efflux into 1 M choline sulfate could be measured with a potassium-sensitive electrode. A typical result might again be in the range of 10 15 mol/(cm2 s). The proton permeability anomaly now becomes clear The same flux is measured for both potassium ion and protons, yet the proton flux is driven by a concentration of protons 6 orders of magnitude less than the concentration of potassium ions. Estimates of the relative permeabilities of the bilayer to protons and potassium using these flux data yield values of 10 6 cm/s for protons and 10 12 cm/s for potassium ion. 

Table VIII. Occurrence of Choline, Choline Sulfate, Mannitol and Ergosterol... 

Species Choline Choline sulfate Mannitol Ergosterol Reference ... 

Choline sulfate, unlike choline [43,45], has been found in all species studied [43,46] (Table VIII). These substances also occur in terrestrial fungi. However, choline sulfate does not seem to be present in phycomycetes (in [43). 

Besides the lichen substances discussed, a number of compounds have been isolated which simply represent general constituents of living cells, biosynthesis of which will not be taken up here. Sufficient to mention choline sulfate and ethanol sulfate esters, with which S-labeling studies have recently been carried out (Feige and Simonis, 1969). Finally, attention should be drawn to a report by Jackson and Keller (1970) on the formation of an unusual ferric oxide mineral through the action by a tropical lichen on basalt as an example of indirect biosynthesis. 

Detoxifica.tlon. Detoxification systems in the human body often involve reactions that utilize sulfur-containing compounds. For example, reactions in which sulfate esters of potentially toxic compounds are formed, rendering these less toxic or nontoxic, are common as are acetylation reactions involving acetyl—SCoA (45). Another important compound is. Vadenosylmethionine [29908-03-0] (SAM), the active form of methionine. SAM acts as a methylating agent, eg, in detoxification reactions such as the methylation of pyridine derivatives, and in the formation of choline (qv), creatine [60-27-5] carnitine [461-06-3] and epinephrine [329-65-7] (50). 

King GM (1984) Metabolism of trimethylamine, choline and glycine betaine by sulfate-reducing and metha-nogenic bacteria in marine sediments. Appl Environ Microbiol 48 719-725. 

Water molecules are absent from the hydrophobic interior, but both the choline and the phosphate headgroups are fully solvated [41]. Similarly, the first hydration shell of the sulfate headgroup of SDS is formed rather by water molecules than by sodium ions. Because of hydration the charge density due to the lipid headgroups is overcompensated by the water dipoles, thereby reducing the transmembrane potential by 50-100 mV across the lipid water interface and resulting in a negative potential at the aqueous side [42]. 

Standard treatment for OPP poisoning is i.v. injection with atropine sulfate to protect the muscarinic end-organs from the accumulation of excessive acetyl choline concentrations. Diagnostic testing, or treatment with atropine must be used cautiously in patients with glaucoma, in view of the risk of increased intraocular pressure from the drug. 

Bacteria glycine betaine, choline-O-sulfate, proline betaine, taurine betaine,... 

---