Enzyme, biosynthesis ethylene

Kende H (1989) Enzymes of ethylene biosynthesis. Plant Physiol 91 1-4. 

Aminocyclopropane-1-Carboxylate Synthase, an Enzyme of Ethylene Biosynthesis... 

The possibility that many organic compounds could potentially be precursors of ethylene was raised, but direct evidence that in apple fruit tissue ethylene derives only from carbons of methionine was provided by Lieberman and was confirmed for other plant species. The pathway of ethylene biosynthesis has been well characterized during the last three decades. The major breakthrough came from the work of Yang and Hoffman, who established 5-adenosyl-L-methionine (SAM) as the precursor of ethylene in higher plants. The key enzyme in ethylene biosynthesis 1-aminocyclopropane-l-carboxylate synthase (S-adenosyl-L-methionine methylthioadenosine lyase, EC 4.4.1.14 ACS) catalyzes the conversion of SAM to 1-aminocyclopropane-l-carboxylic acid (ACC) and then ACC is converted to ethylene by 1-aminocyclopropane-l-carboxylate oxidase (ACO) (Scheme 1). 

Sato, T. Theologis, A. (1989). Cloning the mRNA encoding 1-amino-cyclopropane-l-carboxylate synthase, the key enzyme for ethylene biosynthesis in plants. Proceedings of the National Academy of Sciences (USA) 86, 6621-5. 

Examples of antagonistic interaction include the effects of ABA and auxin on root tip surface charge (Tanada 1972) the effects of ABA and kinetin on coleoptile elongation (Khan and Downing 1968), the effects of GA and tannins on enzyme biosynthesis (Jacobson and Corcoran 1977) and the effects of ethylene and either GA3 or cytokinin on fruit senescence (Goldschmidt et al. 1977). 

Results of Wulf et al (7) show that carrot roots obtained from a supermarket contain myristicin Imperator variety carrots contain an average of 15 parts per million (ppm). Recently harvested, unprocessed carrots only rarely contain myristicin (8). The presence of myristicin in supermarket carrots and its absence in recently harvested ones indicate that its increased concentration may have been induced by some elicitor following harvest. Solar radiation after harvest, or fluorescent lighting during display, may function as such an elicitor. Light is known to produce ethylene and is an activator of phenylalanine ammonia-lyase, one of the regulatory enzymes responsible for phenylpropanoid biosynthesis in plants (9). 

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