Indoleacetic acid production

Indole (I) condenses with formaldehyde and dimethylamine in the presence of acetie acid (Mannich reaction see Section VI,20) largely in the 3-position to give 3 dimethylaminomethylindole or gramine (II). The latter reaets in hot aqueous ethanol with sodium cyanide to give the nitrile (III) upon boiling the reaction mixture, the nitrile undergoes hydrolysis to yield 3-indoleaeet-amide (IV), part of which is further hydrolysed to 3-indoleacetic acid (V, as sodium salt). The product is a readily separable mixture of 20 per cent, of (IV) and 80 per cent, of (V). 

The principal reason that DMT must be administer parenterally is its rapid and efficient metabolism. It can be oxidized to the N-oxide. It can be cyclized to b-carbolines, both with and without an N-methyl group. It can be N-dealkylated to form NMT and simple tryptamine itself. Best known is its oxidative destruction, by the monoamine oxidase system, to the inactive indoleacetic acid. There is a wild biochemical conversion process known for tryptophan that involves an enzymatic conversion to kynurenine by the removal of the indole-2-carbon. A similar product, N,N-dimethylkynuramine or DMK, has been seen with DMT, when it was added to whole human blood in vitro. 

The indole ring system 14 is particularly important and occurs widely in nature. Tryptophan 23 is one of the essential amino acids and is found in most proteins. Its metabolites include tryptamine 24. 3-Indoleacetic acid 25 is an important plant growth hormone. The indole alkaloids, exemplified by yohimbine 26, are an important family of natural products. 

TrvDtoDhol. Tryptophol [12] is a natural product in plants and microorganisms and is involved in indoleacetic acid metabolism. A major metabolite from Drechslera nodulosum. tryptophol was isolated and identified from extracts of culture filtrates of this fungal pathogen (8S). This report was the first to show that this compound was phytotoxic and caused necrotic lesions on goosegrass (Eleusine indica L.), the weed host of this fungus. Necrotic injury in. goosegrass occurred after application of tryptophol at 6.2 x 10 ... 

The relationship between catabolite repression by glucose and induction of cellulase by sophorose has been studied in T. viride by Nisizawa and co-workers (36, 37). The induction by sophorose (10 M) was competitively repressed by glucose and other metabolites such as pyruvate. Since glucose was an effective repressor when added one hour after the previous addition of actinomycin D, it was concluded that the repression takes place at the translational level. Previous work indicated (26) that the sophorose induction led to the formation of a cellulase component designated FII, which is the source of cellulase II discussed below. In higher plants indoleacetic acid (38) and abscisic acid (39) have been shown to stimulate cellulase production. 

LXXXIV) or undergo further oxidation and base-catalyzed decarboxylation (LXXXVI) to the labile nonisolable 3-methyleneoxindole (LXXXVIIa), characterizable as the sodium bisulfate addition product (LXXXVIIb). 8-Methylene oxindole (LXXXVIIa) bears a spectral resemblance to the oxidation product of auxin produced by peroxidase or indoleacetic acid oxidase from the fungus Omphalia ftavida (Ray and Thimann, 1956). 

The plant hormone auxin has been shown to be radiosensitive. The product of the irradiation of auxin (p-indoleacetic acid) is a polymer similar to that obtained in the radiolysis of indole. 

Tryptophan can be converted to indolepyruvic acid either by oxidative deamination or by transamination (e.g., 739, 912) and the indolepyruvic acid can give rise to indoleacetic acid. The fate of indoleacetic acid formed by the bacterial flora of the mammalian gut is discussed below. Bacterial indolelactic acid (e.g., 757) is presumably derived from indolepyruvic acid, but indolelactic acid excreted by mammals (e.g. 17) may be of true mammalian rather than bacterial origin. Indolepropionic acid can also be formed by bacteria (e.g., 412, 633), but further metabolism in mammals of any indolepropionic acid formed in the gut is still obscure (904). Skatole (3-methylindole) has long been known as a product of bacterial decomposition of protein and is formed from tryptophan not only by the bacterial flora of the gut but also in putrefying secretions, e.g., sputum (756). It may well arise by decarboxylation of indoleacetic acid. 

The work of many investigators soon showed it to be extremely widespread in plants, and it became clear that it was a fundamental plant hormone (e.g., reviews 530, 655a). Excessive production of indoleacetic acid by parasites is responsible for certain types of plant tumor (e.g., 948). The synthetic plant growth regulators, which are in general substituted phenoxyacetic acids, probably function as indoleacetic acid analogues. 

Indoleacetic acid is degraded in plants by a specific indoleacetic acid oxidase. This is a light-activatable flavoprotein enzyme coupled through hydrogen peroxide to a peroxidase (285 but cf. 463a, 805b). It apparently uses phenols as cofactors (296) but can be inhibited by polyphenols (305). The product of the reaction is still unidentified (836). 

Tryptophan also gives rise to the important plant hormone, indoleacetic acid, and microorganisms and especially plants metabolize the aromatic amino acids to a wide range of natural products, for example, certain antibiotics, alkaloids (e.g., diagrams 25-28), flavonoids, and possibly lignin. These are briefly considered. 

Ben-Yehoshua, S., Biggs, R.M., 1970. Effects of iron and copper ions in promotion of selective abscission and ethylene production by citrus fruit and the inactivation of indoleacetic acid. Plant Physiol. 45, 604-607. 

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