Organic vegetable soups contained more salicylic acid than non-organic ones, suggesting that the vegetables and plants used to prepare them contained greater amounts of the phenolic acid than the corresponding non-organic ingredients. Consumption of organic foods may result in a greater intake of salicylic acid.

Background Salicylic acid (SA) is present in the serum of people who have not taken salicylate drugs. Now we have examined the urine of these subjects and found that it contains SA and salicyluric acid (SU). We have established the identities of these phenolic acids and determined their concentrations.

Specific degradation of the phospholipid membrane of guinea-pig liver microsomal fraction with phospholipase A inactivated glucuronyltransferase. The inactivation was reversed by phosphatidylcholine and mixed microsomal phospholipid micelles at concentrations similar to those present in intact microsomal preparations. The other commonly occurring phospholipids did not reactivate phospholipase A-treated enzyme. Since the mixed microsomal phospholipids consisted mainly of phosphatidylcholine, it is concluded that the reactivation by phospholipids is phosphatidylcholine-specific. Reactivation was also achieved by low concentrations of the cationic detergents cetylpyridinium chloride and cetyltrimethylammonium bromide. Higher concentrations of these detergents inactivated the glucuronyltransferase activity of intact and phospholipase A-treated microsomal fractions. Anionic detergents were potent inactivators of the glucuronyltransferase activity of untreated and phospholipase A-treated microsomal fractions, whereas non-ionic detergents had little effect on the activity of either preparation. Measurements of the zeta-potentials of the micellar species used in this study showed that no obvious relationship existed between the zeta-potentials and the ability to reactivate glucuronyltransferase. However, high positive or negative zeta-potentials were correlated with the ability of the amphipathic compound to inactivate glucuronyltransferase.

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In order to study the interaction of liver microsomal UDPglucuronosyltransferase and microsomal phospholipids under closely defined conditions, guinea-pig enzyme was purified to homogeneity (as judged by sodium dodecyl sulphate gel electrophoresis) by detergent-solubilisation, salt precipitation, chromatography on DEAE-cellulose and DEAE-Sephadex, and affinity chromatography on UDPglucuronosyl-diaminohexanyl -Sepharose 4B. The purified transferase, which catalysed the glucuronidation of p-nitrophenol with high specific activity, was associated with microsomal phospholipids, and phosphatidylcholine was the major species present ; the transferase protein had a subunit molecular weight of about 55000. The enzyme was almost completely inactivated by delipidation of the protein by hydroxyapatite chromatography and efficient reconstitution of high activity was observed only with fluid (microsomal and egg-yolk) phosphatidylcholines. These results confirm that microsomal UDPglucuronosyltransferase is phospholipid-dependent with a specific requirement for phosphatidylcholine.Liver microsomal U DPglucuronosyltransferase is regulated by the intact phospholipid structure of the microsomal membrane [l, 21 and a large body of data, obtained by studying impure enzyme fractions, indicates that for expression of full activity the enzyme requires phospholipids [3].When microsomal membranes containing non-latent enzyme were treated with phospholipases the transferase was inactivated and activity was restored with dispersions of phospholipid mixtures extracted from the membranes [4-71. Delipidated, unfractionated microsomal protein showed very low transferase activity and re-activation was observed with egg, bovine or soybean phosphatidylcholine, egg or bovine lysophosphatidylcholine, or mixtures of the two phospholipid species [8-131. It was also shown that reconstitution of UDPglucuronosyltransferase activity was associated with binding of phospholipid re-activators to these proteins [I I]. Solubilised, partially-purified rabbit-liver transferase preparations (catalysing the glucuronidation of p-nitrophenol and oestrone) were inactivated by removing phospholipids and their activities were reconstituted with egg, bovinc or synthetic phosphatidylcholine or with cgg lysophosphatidylcholine [14,15]. It has also been reported [I61 that phospholipids were removed from rat-liver transferase fractions during enzyme purification and that the activity of a crude detergentsolubulised enzyme fraction towards bilirubin, but not p-nitrophenol, was supported by egg phosphatidylcholine.In this paper we extend our work on the modulation of U DPglucuronosyltransferase by phospholipids by reporting results of a lipid-depletion/reconstitution study employing a closely defined syslem. We have uscd guinea-pig liver microsomal enzyme purified to apparent homogeneity and purified microsomal phospholipids. The enzyme is shown to be a phospholipid-protein complex whose high activity is specifically dependent upon fluid phosphatidylcholines.

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More than 80% of the phospholipid component of guinea-pig liver microsomal membranes (prepared with 154mM-KCl) was removed by treatment with phospholipase A followed by extraction of the lysophosphatides and fatty acids produced with albumin. Delipidation strongly inactivated the highly active UDP-glucuronyltransferase of these preparations and activity was restored by mixtures of phosphatidylcholine and lysophosphatidylchlone. However, small quantities of lysophosphatides were still associated with the delipidated fractions after extraction with albumin and might have influenced the inactivation and re-activation observed. To eliminate these uncertainties, microsomal proteins and phospholipids were separated by gel filtration on Sephadex G-150 in the presence of cholate. This technique also strongly inactivated the enzyme but did not generate membrane-active phospholipid degradation products. High transferase activity was again restored to the delipidated protein by choline glycerophosphatides. These results confirm the view that the fully active form of microsomal UDP-glucuronyltransferase is phospholipid-dependent.

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