Dependence of in Vivo Ethylene Production Rate on 1-Aminocyclopropane-1-Carboxylic Acid Content and Oxygen Concentrations

Abstract

1-Aminocyclopropane-l-carboxylic acid (ACC) is aerobically oxidized in plant tissues to form ethylene by ethylene-forming enzyme (EFE). The effect of substrate (ACC and oxygen) concentrations on ethylene production rate by plant tissues was investigated. The Km value for 02 in ethylene production varied greatly depending on the internal ACC content. When ACC levels in the tissue were low (below its Km value), the concentration of 02 giving half-maximal ethylene production rate ([Sj.s) ranged between 5 and 7%, and was similar among different tissues. As the concentration of ACC was increased (greater than its Km value), 151.5 for 02 decreased markedly. In contrast, the Km value for ACC was not much dependent on 02 concentration, but varied greatly among different plant tissues, ranging from 8 micromolar in apple (Malus sylvestris Mill.) tissue to 120 micromolar in etiolated wheat (Triticum aestivum) leaf. Such a great variation was thought to be due to the different compartmentation of ACC within the cells in different tissues. These kinetic data are consistent with the view that EFE follows an ordered binding mechanism in which EFE binds first to 02 and then to ACC.to 16% for oxygen (1)(2)(3)8), and from 61 to 500 ,uM for ACC (5,8,11,14), where the ACC concentration refers to the internal concentration of ACC within the tissues or external ACC concentration for the protoplast or vacuole preparations. Although many reports documented the relationship between ethylene production rates and external ACC concentrations in various plant tissues, these values were not considered, because external ACC concentrations do not reflect internal concentrations. Since EFE is a bi-substrate enzyme, the [S] Plant Materials. Apples (Malus sylvestris Mill., var Golden Delicious) were harvested from a local orchard and were stored at 1°C. Apple plugs (1 cm in diameter and 2 cm in length) were prepared with a cork borer and a knife. After floating with shaking in 2% KCI solution for 10 min, plugs were blotted dry and were used in the experiments at room temperature (20°C); they exhibited steady ethylene production rates for at least 3 h.Mungbean (Vigna radiata L.) hypocotyl segments (1 and 3 cm under hook) were prepared from 3-d-old etiolated seedlings grown in paper towel at 25°C in darkness, and used as experimental material.Wheat (Triticum aestivum) seeds were germinated and seedlings grown in vermiculite at 25°C either in light (14 h light/10 h dark cycle) or in darkness for 9 d. Experimental materials consisted of 8-cm long segments cut from the tip of the leaves.Isolation of Protoplast from Barley Leaves. Barley (Hordeum vulgare) seeds were germinated and grown in vermiculite at 25°C in light. After 4 to 5 d, top leaves (3-4 cm) were harvested. The abaxial epidermis of the leaves was peeled off with fine forceps, and the leaves were then floated in a Petri dish with the peeled sides down in 20 mL enzyme solution containing 2% cellulysin (Calbiochem), 1% pectolyase (Seishin Pharmaceutical, Japan), 1% macerase (Calbi...

Role of internal atmosphere on fruit ripening and storability—a review

“…Difference in the depletion of internal O 2 levels in different kind of fruits under MA condition was observed (Sornsrivichai et al 1998). Yip et al (1988) claimed that 50% reduction in ethylene production could be obtained at 1% level of O 2 . This is primarily because of the fact that O 2 is itself a substrate for the reaction catalysed by the enzyme ACC-oxidase (Fig.…”

Ethylene Biosynthesis and Accumulation under Drained and Submerged Conditions (A Comparative Study of Two Rumex Species)

“…In completely submerged terres- (Armstrong et al, 1994;Madsen and Breinholt, 1995). Both carbon dioxide and oxygen are necessary for the conversion of ACC to ethylene (Kao and Yang, 1982;Yip et al, 1988), although carbon dioxide is not part of this reaction (Yang and Hoffman, 1984). Therefore, carbon dioxide and oxygen deficiency reduce the specific activity of ACC oxidase.…”

Increase in ACC oxidase levels and activities during paradormancy release of leafy spurge (Euphorbia esula) buds

“…In addition to ACC, ACO requires O 2 as a substrate, ascorbate as co-substrate, and Fe 2+ and CO 2 as cofactors (Dong et al 1992). Inadequate levels of any of these molecules could have limited ACO activity despite the increase in ACO expression (Yip et al 1988;Sanders and de Wild 2003;Zechmann 2011). At least in excised buds, the results suggest sequential changes in the factors limiting ACO activity after growth induction, with perhaps cofactors limiting at day 3 and ACC at day 4.…”