Site pages
Current course
Participants
General
26 February - 4 March
5 March - 11 March
12 March - 18 March
19 March - 25 March
26 March - 1 April
2 April - 8 April
9 April - 15 April
16 April - 22 April
23 April - 29 April
30 April - 6 May
Ethylene Biosynthesis
Ethylene has been shown to be produced from methionine via a intermediates S-adenosyl-methionine (SAM) and 1-aminocyclopropane-1-carboxylic acid (ACC). The conversion of SAM to ACC by the enzymes ACC Synthase(ACS). In higher plants, ACC can be removed by conjugation to form malonyl ACC (MACC) or glutamyl ACC (GACC). Ethylene forming enzyme (EFE) or ACC oxidase (ACO) is required to convert ACC to ethylene. ACO is a liable enzyme and sensitive to oxygen and attached to outer layer of the plasmalemma. Factor that effect the activity of the ACS includes fruit ripening, senescence, auxin, physical injuries and chilling injury. This enzyme (ACS) is strongly inhibited by aminooxyacetic acid(AOA), rhizobitoxine and amino ethoxy vinayl glycine (AVG). ACO is inhibited by anaerobiosis, temperature above 350C and cobalt ions.
The pattern of C2H4 production in tomato is it rises before the onset of ripening, where as in, apple and mango it does not rise before increase in reparation. Immature tomato fruit has high rate of C2H4 production and it extremely tolerance to C2H4 but banana and melons can readily ripened with C2H4 even when immature.
Ripening is a catabolic process wherein the fruit undergoes a chain of biochemical reactions involving changes in colour, texture and taste. |
Last modified: Tuesday, 26 June 2012, 4:43 PM