Ripening, hormones and

Ethylene (C2H4) is the starting material for the preparation of polyethylene. Although typically made during the processing of petroleum, ethylene occurs naturally as a fruit-ripening hormone and as a component of natural gas. 

Several alkenes occur naturally in living organisms. Some of these alkenes act as hormones and control biological functions. Plants produce ethene as a hormone to stimulate flower and seed production and to ripen fruits. Ethene stimulates enzymes in the plants to convert starch and acids of unripe fruit into sugars. The enzymes also soften fruit by breaking down pectin in cell walls. 

Feedback Relationship Between Ethylene and Other Plant Hormones If ethylene production in ripening fruit is an index of aging and senescence, then its suppression should result in retardation, or antagonism to ripening, aging, and senescence. 

Aminocyclopropanecarboxylic acid (74) has attracted special interest (a) as a modified model of natural a-amino acids, in the synthesis of bioactive peptide analogs, potential enzyme inhibitors , or e.g. a derivative with sweetness receptor activity s and (b) together with its Schiff-base metal complexesas the biosynthetic precursor of ethene, the plant ripening hormone . (See these sources and the review in Reference 135 for further references.)... 

Usually, donor and acceptor functions are located at different ring carbon atoms, but there are also examples in which both functions are linked to the same atom. The most prominent compound of this type is 1-aminocyclopropanecarboxylic acid (ACC, 6), a naturally occurring amino acid which is the precursor of the fruit-ripening hormone ethene. In fruit tissues, such as apple tissue, this amino acid is oxidized to ethene, carbon dioxide and hydrogen cyanide by the enzyme ACC oxidase, also known as ethene-forming enzyme (EFE). This reaction has been studied in detail. ... 

Ethylene occurs naturally in petroleum and natural gas, but only to a very small percentage. It also occurs naturally in plants where it functions as a hormone and has a number of important effects on the growth and development of plants. These effects have been used for thousands of years, although the chemical mechanism involved was not understood. For example, the ancient Chinese are said to have burned incense in closed containers in order to facilitate the ripening of pears. Although they were certainly not... 

Enzymes may also catalyze transformations of a highly selective and nniqne natnre snch as in transformations of small molecnles. Examples are the fragmentation of 1-amino-cyclopropane-1-carboxylate to the frnit ripening hormone ethylene, the cycloreversion of thymine dimers in DNA repair, the synthesis of isopenicUhn and the rednction of molecn-lai nitrogen (N2) to ammonia... 

Real-World Reading Link Plants produce ethene as a natural ripening hormone. For efficiency in harvesting and transporting produce to market, fruits and vegetables are often picked while unripe and are exposed to ethene so they will ripen at the same time. 

I04"C) is often considered as a plant growth substance because it acts like a fruit-ripening hormone. The biosynthesis of ethylene in the plant from 1 -ami-nocyclopropanecarboxylic acid is stimulated by auxins abscisic acid and cytokinins can - depending on the type of plant - have stimulating or inhibiting effects, and tissue injuries in plants lead to the formation of the so-called wound ethylene . For information on the numerous roles of ethylene, see Other... 

Biological activity P. are toxic to the corpora allata of insects and directly inhibit thereby the biosynthesis of juvenile hormones, and thus the larvae prematurely develop into pupa (Latin praecox=premature). In adults, egg ripening and thus the ability to reproduce is principally affected. The synthetic, so-called P. Ill (proallatocidin, 6-ethoxy-7-methoxy-2,2-dimethyl-2//-1-benzopyran), C,4H,g03, Mr 234.30, oil, bp. 109°C (13 Pa), has a 10-fold stronger activity than P. 11. ... 

Ethylene is also found in plants, where it is a hormone that controls seedling growth and regulates fruit ripening. The discovery of this property led to the use of ethylene by food processors for ripening fruits and vegetables after harvest. 

Chloroethylphosphonic acid, Ethrek Q-CH2-CH2-P0(0H)2, a synthetic growth regulator, which generates ethylene (fruit ripening hormone). It is used for the loosening of Primus its, and to stimulate the flowering of pineapple. 

The classic P. are Auxins (see), Cibberellins (see), Antheridiogen (see), Cytokinins (see), Abscisic acid (see). Flowering hormone (see) and Fruit ripening hormone (see). 

Flaishman, M.A. and Kolattukudy, RE. (1994) Timing of fungal invasion using host s ripening hormone as a signal. Proc. Natl. Acad. Sci. USA, 91, 6579-6583. 

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