Acetic acid biosynthesis from

Use of Mutants in Biosynthetic Studies Formation of Chorismic Acid Derivatives of Chorismic Acid Biosynthesis of Tryptophan Indole 3-Acetic Acid Avenalumins from Oats DIMBOA and Related Compounds Biosynthesis of Phenylalanine and Tyrosine Compounds Derived from Shikimic Pathway Intermediates... 

Fig. 7.6. Biosynthesis of indole acetic acid (modified from Smith, 1980 used with permission of the copyright owner, Springer-Verlag, Berlin).

TABLE 1. Analysis by Schmidt degradation to predict biosynthetic pathways for fatty acid biosynthesis from [2- C]acetate in various oil seeds. 

Table 7 Inhibition by sethoxydim of fatty acid biosynthesis from 2- C-acetate in isolated maize chloroplasts (after 33),...

Plastids were incubation under optimum conditions for fatty acid biosynthesis from acetate [6]. 

The introduction to Section 26 8 pointed out that mevalonic acid is the biosynthetic pre cursor of isopentenyl pyrophosphate The early steps m the biosynthesis of mevalonate from three molecules of acetic acid are analogous to those m fatty acid biosynthesis (Sec tion 26 3) except that they do not involve acyl earner protein Thus the reaction of acetyl coenzyme A with malonyl coenzyme A yields a molecule of acetoacetyl coenzyme A... 

Problem 29.5 Evidence for the role of acetate in fatty-acid biosynthesis comes from isotope-labeling experiments. If acetate labeled with 13C in the methyl group ( CFtyCC H) were incorporated into fatty acids, at what positions in the fatty-acid chain would you expect the, 3C label to appear ... 

The tetramerization of suitable monopyrroles is one of the simplest and most effective approaches to prepare porphyrins (see Section 1.1.1.1.). This approach, which is best carried out with a-(hydroxymethyl)- or ot-(aminomethyl)pyrroles, can be designated as a biomimetic synthesis because nature also uses the x-(aminomethyl)pyrrole porphobilinogen to produce uroporphyrinogen III. the key intermediate in the biosynthesis of all kinds of naturally occurring porphyrins, hydroporphyrins and corrins. The only restriction of this tetramerization method is the fact that tnonopyrroles with different -substituents form a mixture of four constitutionally isomeric porphyrins named as porphyrins I, II, III, and IV. In the porphyrin biosynthesis starting from porphobilinogen, which has an acetic acid and a propionic acid side chain in the y6-positions, this tetramerization is enzymatically controlled so that only the type III constitutional isomer is formed. 

However, more-rigorous treatment (5% acetic acid, 100°C, 17 hours) opened the imidazole ring and produced /V -cyclohexyl-a-formylaminoacetamidine (57), characterized as the crystalline picrate. Amidine 57 produced no dye in the Bratton-Marshall assay. The same behavior can be expected from AIR (46), although the product of hydrolytic ring-opening was not actually isolated. On the other hand, it was observed that a solution of AIRs (0.2 mM in 0.01-M ammonium hydroxide) prepared by biosynthesis, when stored at 4°C, did not change appreciably within a day. A decrease in the concentration of AIRs of about 30% occurred within a month. 

Ketene dimer (28), made from [ " Cl-labelled acetic acid, has been used to make doubly labelled mevalonic lactone (29) for studies on the biosynthesis of terpenes. Note... 

Additional hypotheses concerning prostaglandin biosynthesis in P. homomalla resulted from isolation of 11R-HETE (76) from the polar lipid fraction [95]. Apparently, 11R-HETE (76) is also a minor product of incubations of arachidonic acid with acetone powder preparations of P. homomalla [95], In this alternate hypothesis (Scheme 8), an 11-hydroxy or 11-hydroperoxy-8,9-allene oxide intermediate is formed from a sequence of oxidations at C8 and Cll. Opening of the allene oxide to a transient C8 earboeation induces eycli-zation with a consequent addition of water to C15. This proposed pathway leads initially to formation of PGE2 (16 or 38), which following acetylation, elimination of acetic acid from Cl 1-12, and esterification, forms the observed major natural product in the coral, 15-acetoxy methyl PGA2 (36 or 54). Notably, if... 

Yu and Wang431 considered that indole-3-acetic acid exerts its stimulating effect on expansion growth by inducing the synthesis of the enzyme catalyzing the conversion of S-adenosylmethionine into ACC, a conclusion at variance with the suggestion of Vioque and coworkers432 that indoleacetic acid oxidase and its substrate (IAA) participate in the last reaction in the ethylene biosynthesis pathway, namely, the formation of ethylene from ACC. 

Carboxylic acids, compounds of the type RCOH, constitute one of the most frequently encountered classes of organic compounds. Countless natural products are carboxylic acids or are derived from them. Some carboxylic acids, such as acetic acid, have been known for centuries. Others, such as the prostaglandins, which are powerful regulators of numerous biological processes, remained unknown until relatively recently. Still others, aspirin for example, are the products of chemical synthesis. The therapeutic effects of aspirin, welcomed long before the discovery of prostaglandins, are now understood to result from aspirin s ability to inhibit the biosynthesis of prostaglandins. 

Hygrine.—The alkaloid hygrine (3) is an intermediate in the formation of tropane bases. Biosynthesis is from acetic acid, plausibly via acetoacetic acid (cf. Vol. 10, p. 12), and from ornithine (1), very reasonably in the manner shown in Scheme l.1,2 Acetoacetate has been confirmed as an intact precursor for hygrine in experiments with [3-14C]- and [4-14C]-acetoacetic acid in Nicandra phys-aloides. Labelling in (3) was, respectively, of C-2 and C-3, which confirms the suspected orientation of acetoacetate in hygrine (see Scheme l).3... 

Slaframine.—Slaframine (37) is produced by the phytopathogen Rhizoctonia leguminicola. It has been known for some time that (37) derives in part from lysine via pipecolic acid (33), which is incorporated intact the earliest bicyclic intermediate identified is (38) (c/. Vol. 5, p. 9 and ref. 2). New results have shown that the two skeletal carbons in (37), and also in the metabolite (36), not accounted for by pipecolic acid, derive from malonate (and acetate).13 The labelling of (37) by, in particular, [2-2H2]acetate was deduced to be of C-2 on the basis of mass spectral evidence (which is not entirely convincing). The acyl-CoA derivative (34) has been suggested as an intermediate in the biosynthesis of (37) and also of (36). It is to be noted that condensation between malonyl-CoA and pipecolic acid (33) to give (34) must be simultaneous with decarboxylation of malonyl-CoA, since two deuterium atoms of acetate are retained at C-2 in (37) (later intermediates with a double-bond to C-2 are also excluded by these results). 

Nitrilase was initially discovered in plants as an enzyme involved in the biosynthesis of the plant hormone indole-3-acetic acid (IAA) [74,75], Recently, four genes of nitrilases (belonging to arylacetonitrilase) involved in the IAA biosynthesis have been cloned and characterized from Arabidopsis thaliana [76-78], After the discovery of the plant nitrilase in 1964, various nitrilases were purified and characterized [41], Nitrilases are roughly classified into three major categories according to substrate specificity (i) aromatic nitrilase, which acts on aromatic or heterocyclic nitriles (ii) aliphatic nitrilase, which acts on aliphatic nitriles (iii) arylacetonitrilase, which acts on arylacetonitriles. These three types... 

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