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Two types of bovine pituitary gland polyprenols were resolved by silica gel chromatography; i. e., the high molecular weight dolichols of 17 to 23 isoprene units with the OH-terminal isoprene residue saturated, and a fully unsaturated decaprenol. The latter compound was found to be a mixture of molecules differing in the proportion of cis - and trans - isoprene units.

InNeurospora crassa, phospholipids containing ethanolamine, monomethylaminoethanol, dimethylaminoethanol and choline are formed by a pathway involving cytidine nucleotides. The rate of formation of these phospholipids does not appear to be dependent on the fatty acid composition of diacylglycerols acting as acceptors of phosphorylated aminoethanols. The presence of choline in the growth medium represses the activity of enzymes of the methylation pathway for the biosynthesis of 1,2-diacyl-sn-glycero-3-phosphorylcholine (diacyl-GPCh) and induces the activity of enzymes of the cytidine mechanism.

The ability of rat liver microsomes to catalyze UDP-glucuronic acid-dependent glucuronidation of monohydroxy-bile acids was examined. The following bile acids were used as substrates, each as the 3 alpha and 3 beta epimer: 3-hydroxy-5 beta-cholanoic acid (C24), 3-hydroxy-5 beta-norcholanoic acid (C23), 3-hydroxy-5 beta-bisnorcholanoic acid (C22), 3-hydroxy-5 beta-pregnan-21-oic acid (C21), and 3-hydroxy-5 beta-androstane-17 beta-carboxylic acid (C20). The corresponding glucuronides were chemically synthesized to serve as standards and were characterized by thin-layer and gas-liquid chromatography as well as by nuclear magnetic resonance. Enzymatic glucuronidation reactions were optimized with respect to pH for each product formed and the kinetic parameters for each reaction were measured. Analytical techniques necessary to separate products from unreacted substrates and to identify them included thin-layer chromatography, gas-liquid chromatography, and nuclear magnetic resonance. It was found that the 3 alpha epimers of the five bile acids listed above enzymatically formed 3-O-glucuronides, C24 being the best substrate, followed by C21 and C20; C22 and C23 gave rise to only small amounts of this product. The 3 beta epimers of all bile acids tested were poorer substrates, although by a factor that varied widely. In addition to the expected hydroxyl-linked glucuronide, three of the 3 alpha-bile acids (C23, C22, and C20) and at least one 3 beta-bile acid (C20), gave rise to a novel metabolite in which the 1-OH of glucuronic acid was esterified with the steroidal carboxyl group (carboxyl-linked glucuronide).

A series of 3-monohydroxylated bile acids, in unlabeled and radioactive form, of varying side chain length and configuration at C-3 has been synthesized and rigorously characterized. They include: 3 alpha- and 3 beta-hydroxy-5 beta-androstane-17 beta-carboxylic acids (C20); 3 alpha- and 3 beta-hydroxy-5 beta-pregnan-21-oic acids (C21); 3 alpha- and 3 beta-hydroxy-23,24-bisnor-5 beta-cholan-22-oic acids (C22); 3 alpha- and 3 beta-hydroxy-24-nor-5 beta-cholan-23-oic acids (C23, norlithocholic and isonorlithocholic acids); and 3 beta-hydroxy-5 beta-cholan-24-oic acid (C24, isolithocholic acid). A novel approach to the degradation of lithocholic acid acetate to 24-norlithocholic acid is described. This degradation involves the photochemical modification of a Hunsdiecker reaction and Kornblum oxidation of the intermediate 23-bromide. The availability of these compounds makes it possible to study the metabolism and biological effects of short chain bile acids.

It has been observed that a dolichol, alpha dihydro-undecaprenol, induces phenotypic changes in Ehrlich ascites tumour [EAT] cells. In the presence of this dolichol in the medium. EAT cells attach to glass and spread on it but grow in an overlapping pattern. This spreading takes place after a lag of between 72-96 hours at continuous exposure to the dolichol. When cells, once induced to spread, are trypsinized, they can spread once more within 3-6 hours in the dolichol-free medium. It is suggested that dolichols, which act as lipid intermediates in protein glycosylation, may represent a class of compounds which by interference with the biosynthesis of plasma membrane constituents influence surface properties of EAT cells and induce spreading. The results presented in this paper support the view that sugar moieties of plasma membrane constituents play a role in controlling cell attachment, spreading, and intercellular communication.

Phosphoethanolaminetransferase of high specific activity was solubilized from rat liver microsomes with the non-ionic detergent octyl glucoside. The solubilization method is fast and simple, allowing for processing of large amounts of material. The solubilized enzyme is stable. It contains virtually no phosphocholinetransferase activity. A preliminary characterization of the enzyme, with both diacyl- and alkylacyl-glycerol as substrate, is given. For the reaction, the lipid substrates were incorporated into artificial phospholipid bilayers (liposomes).

Although harderian glands are rich in neutral glycerolipids with ether bonds, less than 20% of the choline glycerophospholipids have ether bonds in the white and pink portions of the adult rabbit harderian gland. Only 6% of these are plasmalogens while 94% are alkylacyl glycerophosphocholines. The ethanolamine glycerophospholipids include 37% with ether bonds in both white and pink portions. In the white portion 96% are plasmalogens but only 19% are plasmalogens in the pink portion. The microsomal ethanolaminephosphotransferase (EC 2.7.8.1) is more active with diacylglycerols than with alkylacylglycerols. The microsomal cholinephosphotransferase (EC 2.7.8.2) is equally active with both diradylglycerols. Particularly with microsomes from the pink portion, the apparent K m values for CDPethanolamine and CDPcholine are lower in the presence of alkylacylglycerols than in the presence of diacylglycerols. The incorporation of radioactivity from CDP[ 14 C]ethanolamine and CDP[ 14 C]choline into ethanolamine and choline plasmalogens was increased several-fold by addition of alkylacylglycerols but was not increased substantially by addition of diacylglycerols.

Transfer of fatty acids from phospholipids to polyprenols, catalysed by the transacylase from rat liver microsomes, was investigated. The specificity of the enzyme for polyprenols of different chain length and different degree of saturation was studied using individual isoprenologues, the preparation of which in highly tritiated form is described. It was found that short-chain polyprenols are better substrates for the enzyme than long-chain polyprenols, and alpha-saturated better than unsaturated or multiply saturated polyprenols. Short-chain, alpha-saturated single isoprenologues were several-fold more active as acyl acceptors than natural dolichol.

The glucuronidation of 6-hydroxylated bile acids by human liver microsomes has been studied in vitro; for comparison, several major bile acids lacking a 6-hydroxyl group were also investigated. Glucuronidation rates for 6 alpha-hydroxylated bile acids were 10-20 times higher than those of substrates lacking a hydroxyl group in position 6. The highest rates measured were for hyodeoxy- and hyocholic acids, and kinetic analyses were carried out using these substrates. Rigorous product identification by high-field proton nuclear magnetic resonance and by electron impact mass spectrometry of methyl ester/peracetate derivatives revealed that 6-O-beta-D-glucuronides were the exclusive products formed in these enzymatic reactions. These results, together with literature data, indicate that 6 alpha-hydroxylation followed by 6-O-glucuronidation constitutes an alternative route of excretion of toxic hydrophobic bile acids.