Aromatic substances, biosynthesis

The shikimate pathway was identified through the study of ultraviolet light-induced mutants of E. coli, Aerobacter aerogenes, and Neurospora. In 1950, using the penicillin enrichment technique (Chapter 26), Davis obtained a series of mutants of E. coli that would not grow without the addition of aromatic substances.4 5 A number of the mutants required five compounds tyrosine, phenylalanine, tryptophan, p-aminobenzoic acid, and a trace of p-hydroxybenzoic acid. It was a surprise to find that the requirements for all five compounds could be met by the addition of shikimic acid, an aliphatic compound that was then regarded as a rare plant acid. Thus, shikimate was implicated as an intermediate in the biosynthesis of the three aromatic amino acids and of other essential aromatic substances.6 7... 

The 8 C-values found for natural aromatic substances from Cj-plants are usually within the range of -26 to -32%o, while the deuterium content of these products (8 H -50 to -150%o) is relatively close to that of the carbohydrates of the same origin (8 H -30 to -170%o), even though in special cases biochemical reduction steps in the course of the biosynthesis of these products may be accompanied by remarkable deuterium depletions [245, 246[. Secondary modifications (oxidation, methylation) usually cause only small additional fractionations of the hydrogen isotopes. 

The tryptophan biosynthetic pathway in microorganisms is one of the branches from a common pathway for the biosynthesis of the aromatic substances. Some regulation of tryptophan synthesis occurs at the level of the common aromatic pathway as well as at the level of the synthesis of glutamine [1,2], a tryptophan precursor. This chapter will be... 

Tanenbaum, S. W., and E. W. Bassett The biosynthesis of patulin. I. Related aromatic substances from Penicillium patulum, strain 2159 A II, the general physiology of several strains of P. patulum. Biochim. et Biophys. Acta 28, 21, 247 (1958b). 

Bu Lock, J. D., and H. M. Smalley Biosynthesis of aromatic substances from acetyl and malonyl-coenzyme A. Proc. Chem. Soc. 1961, 209. 

Cynarine is the main active agent of artichoke extract. It is a cinnamic acid derivative the substitution pattern of its aromatic rings is similar to that of dopamine. Caffeic acid is also regarded as a major active substance. It has not yet been clarified to which constituents the known modes of action are attributable .) increase in choleresis, (2.) inhibition of cholesterol biosynthesis, (3.) hepatoprotection due to antioxidative effects, and (4.) activation of the urea cycle. 

According to one theory, the synthesis of humic substances is supposed to be brought about, primarily, by the condensation of the autolysis products from micro-organisms growing on carbohydrates (mostly cellulose). The biosynthesis of aromatic compounds from carbohydrates " may be of importance in the soil. 

Thin layer chromatographic analysis is also highly applicable to the determination of aromatic organic acids.In human organisms, aromatic acids are synthesized as metabolites in intoxication by toluene, xylene, and ethyl benzene. These compounds are easily absorbed through the skin or respiratory system, and are oxidized to aromatic acids. The separation, identification, and quantitative analyses of aromatic acids are also necessary because they appear as semiproducts of the biosynthesis of aromatic amino acids in plants (phenolic acids), and metabolites of numerous toxic substances, drugs, and catecholamines. Polar adsorbents and polar-... 

In discussing the use of mutants of microorganisms in the study of aromatic biosynthesis it was pointed out that valuable information could thus be obtained. An organism with a metabolic block rendering it unable to convert a substance X into its metabolite Y is likely either to excrete X, or to metabolize X by an alternative pathway if such is available, or to excrete metabolites of X formed by the action of relatively unspecific detoxicating systems. Accumulation or excretion of abnormal substances may therefore indicate an enzymic deficiency of this type. In the latter part of... 

Two interesting metabolites of Penicillium patulum are patulin and penicillic acid. Their biosynthesis involves the cleavage of an aromatic ring. These substances are mycotoxins and their activity in this context is discussed in Chapter 9. 

One of the major achievements in all of science has been the identification, at the molecnlar level, of the chemical interactions that are involved in the transfer of genetic information and the control of protein biosynthesis. The substances involved are biological macromolecnles called nucleic acids. Nucleic acids were isolated over 100 years ago, and, as their name implies, they are acidic substances present in the nuclei of cells. There are two major kinds of nucleic acids ribonucleic acid (RNA) and deoxyribonucleic acid (DNA). To understand the complex structure of nucleic acids, we first need to examine some simpler substances, nitrogen-containing aromatic heterocycles called pyrimidines and purines. The parent substance of each class and the numbering system used are shown ... 

V-arachidonoyl-dopamine (NADA, 27) is an endogenous capsaicin-like substance in mammalian nervous tissues. NADA activates cannabinoid CB, receptors, but not dopamine D1 and D2 receptors (Bezuglov et al., 2001 Bisogno et al., 2000). NADA occurs in nervous tissues, with the highest concentrations being found in the striatum, hippocampus, and cerebellum and the lowest concentrations in the dorsal root ganglion (Chu et al., 2003). Proposed mechanisms of NADA biosynthesis include the condensation of AA with tyrosine and the subsequent conversion of A-arachidonoyl-tyrosine to NADA by tyrosine hydroxylase and L-aromatic amino acid decarboxylase. 

Biosynthesis The aromatic hydroxycarboxylic acid is first formed from polyacetates and then esterified enzymatically. Besides in lichens, D. also occur in tanning substances, e.g., in coffee or savory a well-known representative is digallic acid (see tannins). Lit. Culberson Karrer, No. 1023-1053 Zechmeister 41, 1-46 45, 103-234. 

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