The structure of an inhibitor of cholesterol biosynthesis isolated from barley

Purification of the oily, nonpolar fraction of high protein barley (Hordeum vulgare L.) flour by high pressure liquid chromatography yielded 10 major components, two (I, II) of which were potent inhibitors of cholesterogenesis in vivo and in vitro. The addition of purified inhibitor I (2.5-20 ppm) to chick diets significantly decreased hepatic cholesterogenesis and serum total and low density lipoprotein cholesterol and concomitantly increased lipogenic activity. The high resolution mass spectrometric analysis and measurement of different peaks of inhibitor I gave a molecular ion at m/e 424 (C29H44O2) and main peaks at m/e 205, 203, and 165 corresponding to C13H17O2, C13H15O2, and C10H13O2 moieties, respectively. which are characteristic of d-alpha-tocotrienol. This identification was confirmed against synthetic samples. The tocotrienols are widely distributed in the plant kingdom and differ from tocopherols (vitamin E) only in three double bonds in the isoprenoid chain which appear to be essential for the inhibition of cholesterogenesis.     

The biosynthesis of patulin

The biosynthesis of the antibiotic patulin (II) from 6-methylsalicyclic acid (6-MSA) (I) in replacement cultures of Penicillium patulum has been examined with ²H and ${}^{14}\text{C}{}^3\text{H}\text{-labeled}$ intermediates. Efficient utilization of m-cresol (IX), m-hydroxybenzyl alcohol (V), m-hydroxybenzaldehyde (XII), gentisaldehyde (VIII), and gentisyl alcohol (VI) could be demonstrated. Toluquinol (X), although inactive as a precursor of patulin, is converted by refloated cultures of P. patulum to desoxyepoxydon (XIII). Para-hydroxylation of m-cresol proceeds with loss of deuterium at the p-position. Side chain labeling of the aromatic precursors is lost in the conversion. A major portion of this work has been reported in preliminary form (1, 2).     

The biosynthesis of ectoine

Abstract The biosynthetic pathway of the novel compatible solute ectoine (1,4,5,6-tetrahydro-2-methyl-4-pyrimidine carboxylic acid) was studied in the two extremely halophilic eubacteria Ectothiorhodospira halochloris and Halomonas elongata . The pathway starts with the phosphorylation of l -aspartate and shares its first two enzymatic steps with the biosynthesis of amino acids of the aspartate family: aspartokinase and l -aspartate-β-semialdehyde dehydrogenase. Evidence is presented for the presence of the enzymes l -diaminobutyric acid transaminase and l -diaminobutyric acid acetyl transferase and for the new enzyme the ring-forming ectoine synthase.     

The biosynthesis of methionine

Summary The methylation of the thiol group of homocysteine leading to methionine is a biochemical reaction of particular interest since it represents a crossroad of the action of two vitamins, folic acid and cobalamin, both in bacteria and in animals. This enzymic reaction, its mechanism and its regulation which has been studied in detail in several laboratories is discussed. Another route which does not require cobalamin occurs in bacteria and plants. Bacteria possessing both pathways of methionine synthesis show regulatory interconnections between them. Plants which generally are devoid of cobalamin synthesize methionine solely by the cobalaminindependent pathway the mechanism of which is as yet not fully understood.an invited article.     

The biosynthesis of dicoumarol

Micro-organisms have been isolated that can utilize o-coumaric acid as a sole carbon source with the subsequent production of 4-hydroxycoumarin and dicoumarol. One of these organisms, Penicillium jenseni, has been used to examine the biosynthesis of dicoumarol. Certain thermophilic fungi have also been found that can convert o-coumaric acid into dicoumarol.