Biosynthesis of ethylene

Selectively deuterated 1-aminocyclopropanecarboxylic acid ACC 71 was prepared to investigate the biosynthesis of ethylene in plants [105 a] and of ammonia and 2-ketobutyrate in Pseudomonas [105bj. 

Another hormone that can be affected by phenolics is ethylene. Coumaric acid is necessary as a cofactor for the biosynthesis of ethylene [33]. On the other hand, caffeic acid inhibits an enzyme (peroxidase type) for which the cofactor is /7-coumaric acid. Therefore, the balance between /7-coumaric and caffeic acid can in theory influence the regulation of ethylene biosynthesis [6]. 

On the other hand, the impact of ethylene in the composition of headspace gases fed to Taxus sp. cultures was very evident. The positive involvement of ethylene was also noted when cultures were elicited with both dissolved and volatilized methyl jasmonate and with chitin- and chitosan-derived oligosaccharides. The effect of the latter compounds on biosynthesis of ethylene by the plant cell cultures brings us to a better understanding of the interdependence of elicitor and hormone concentrations and of cross-talk signal transduction in plants. 

The effect of homoBR on flowering tissues was to produce bisexual and pistillate flowers on a staminate inflorescence. Also, sepals were deformed (24), and one would suspect some of these effects were due to induced ethylene biosynthesis, as the dosage of the brassinosteroid used was very high. Excess hormone levels are known to induce the biosynthesis of ethylene BR can also do this, and it interacts with auxin and cytokinin in the induction (43). BR can also affect endogenous auxin and abscisic acid levels in treated tissue (21,44,45). Thus BR does have multiple and modulatory effects. 

Another catabolic pathway is transamination (Fig. 24-25, rection h) to 3-mercaptopyravate. The latter compound can be reductively cleaved to pyruvate and sulfide. Cysfeine can also be oxidized by NAD and lacfafe dehydrogenase to 3-mercaptopyruvate. An interesting PLP-dependent p-replacement reaction of cysfeine leads to P-cyanoalanine, the lathyritic factor (Box 8-E) present in some plants. This reaction also detoxifies the HCN produced during the biosynthesis of ethylene from ACC. 

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... 

T. Galliard and H. W. -S. Chan Biosynthesis of Ethylene S. F. Yang and D. O. Adams Biosynthesis of Saturated and Unsaturated Fatty Acids P. K. Stumpf... 

Fig. 13.17. Biosynthesis of ethylene and l-aminocyclopropane-l-carboxylic acid (ACC) and the biosynthesis of ethylene (modified from / Yang, 1984) used with permission of the copyright owner, the American Society of Plant Physiology, Rockville, MD).

Yang, S. F., Biosynthesis of ethylene and its regulation, in Recent Advances in the Biochemistry of Fruits and Vegetables (J. Friend and M. J. C. Rhodes, eds.). Annual Proceedings of the Phytochemistry Society of Europe No. 19), 89-106, Academic Press, London, 1981. 

Many reviews on general ethylene physiology and fruit ripening are available (Burg, 1962 Pratt and Goeschl, 1969 Abeles, 1973 Pratt, 1975). In this chapter we shall deal with the biochemical mechanism by which the double bond is introduced in the biosynthesis of ethylene, the simplest alkene in nature. 

Fig. 1. A postulated mechanism for the biosynthesis of ethylene from methionine. The substituted pyridine c arboxaldehyde stands for pyridoxal phosphate. The scheme is modified from that of Adams and Yang (1979).

The biosynthesis of ethylene has been reviewed recently [9, 33]. In this paper we describe research progress that has occurred since then with regard to (a) ACC synthase, (b) ACC oxidase, (c) ACC N-malonyltransferase, and (d) the methionine cycle, as they related to ethylene biosynthesis. 

The final step in the biosynthesis of ethylene is catalyzed by ACC oxidase. Application of ACC to most plant tissues results in a marked increase in ethylene production, indicating that ACC oxidase in these tissues is constitutive and not rate-limiting. Although ACC-dependent ethylene production is readily demonstrated in intact tissues, in vitro ACC oxidase activity has not been demonstrated independent of intact cellular material. Although intact protoplasts and vacuoles retained the characteristics of tissue ACC oxidase activity [9], Porter and John [24] reported that their preparations retained less than 5% of the activity associated with the parent tissue. They proposed that full ACC oxidase activity requires tissue integrity in addition to the previously noted cell membrane integrity. 

Yang SF, Adams DO (1980) The biosynthesis of ethylene. In Stumpf PK, Conn EE (eds) The biochemistry of plants— A comprehensive treatise. Vol 4, Lipids Structure and function. Academic Press, New York, pp 163-175 Zeevaart JAD (1978) Phytohormones and flower formation. In Letham DS, Goodwin PB, Higgins TJV (eds) Phytohormones and the related compounds— A comprehensive treatise. Vol II. Elsevier/North Holland, Amsterdam, pp 291-327... 

The reaction pathway 18.45 is suggested for the biosynthesis of ethylene (R-CHO pyridoxal phosphate Ad adenosine). 

The aminopropyl transfer from dcSAM results in the release of 5 -methylthio-adenosine (MTA), which is rapidly metabolized and recycled to the SAM precursor methionine in a cyclic pathway known as the methionine salvage cycle (Sauter et al. 2013). MTA is also released from SAM in the biosynthesis of ethylene and nicoti-anamine and considered a toxic metabolite because of product inhibition. A study has shown that MTA affects the synthesis of polyamines (Waduwara-Jayabahu et al. 2012). 

Apelbaum A, Burgoon AC, Anderson JD, Lieberman M, Benarie R, Mattoo AK (1981) Polyamines inhibit biosynthesis of ethylene in higher plant tissue and Iruit protoplasts. Plant Physiol 68 453-456... 

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