β-Alanine as an Ethylene Precursor. Investigations Towards Preparation, and Properties, of a Soluble Enzyme System From a Subcellular Particulate Fraction of Bean Cotyledons

Abstract

Abstract. A method is described for the preparation, from a subcellular particulate fraction of wax bean cotyledons, of a soluble enzyme system that is capable of converting 3-alanine to ethylene. In the presence of ATP, CoA, thiamine pyrophosphate, MgSO4, and pyridoxal phosphate, ethylene production is maximum at a 0.5 mNi concentration of 8-alanine. The system exhibits a pH optimum at 7.0 but when the pH is raised above 8, evolution of the volatile again increases and continues to do so up to pH 12. The enzyme system is stimulated by either NADPH or NADH; the concentration of NADPH necessary to obtain maximum activity is twice that of NADH. The requirement for a reducing agent is in agreement with the proposal that malonate semialdehyde, formed by an aminotransferase reaction from f3-alanine, is reduced to 83-hydroxypropionate. Both malonate semialdehyde and /-hydroxypropionate are better stimulators of production of the volatile in the soluble system than is f3-alanine, and .8-hydroxypropionate is a better stimulator than malonate semialdehyde. This system is also able to incorporate tritium from tritiated water into ethylene; this supports the proposal that ethylene is formed by the decarboxylation of acrylate, the latter being formed from f3-hydroxypropionate.Experiments with both cold and labeled malonate suggest that this compound stimulates ethylene production by acting as an end product inhibitor that prevents the loss of 'Malonate semialdehyde from the pathway. Malonate does not appear to serve as a precursor.Addition of cytopl-asmic enzymes to the enzymes) results in a considerable boost in (mdul/mg protein) is lowered from that of the 'soluble system' (prepared from particulate ethylene production, but the specific activity particulate enzymes alone.

Methods for the Quantification of Ethylene Produced by Plants

“…This problem can be overcome by selectively collecting ethylene on a solid support such as silica gel (Stinson and Spencer 1969;Eastwell et al 1986). Figure 5 gives a diagrammatic representation of this method.…”

Comparison and Evaluation Methods for the Removal of Ethylene and Other Hydrocarbons from Air for Biological Studies

“…The catalysts tested (methods [20][21][22] can be used in various forms. Platinum is commercially available in a variety of concentrations on several different solid support materials, which may be in the form of granules, pellets, fibers, or powders.…”

“…Finely powdered iodine pentoxide (method 16) was added directly to the silica gel. Selenium oxide reagent (method 23 10 40X aqueous formaldehyde in concentrated sulphuric acid (3.3 100) 22 25 11 40% aqueous formaldehyde in fuming sulphuric acid (3.3 100)…”

“…The liquid traps (methods 10 and 11) consisted of 10 ml of reagent in a small gas-washing tube; the air was dispersed through a fritted glass aerator. The solid reactive materials (methods [12][13][14][15][16][17][18][19][20][21][22] were packed in a stainless steel tube (45 x 1.27 cm o.d.). Elevated temperatures, when required, were attained with a semimicrocombustion furnace (Sargent-Welch Scientific Co.) with a heating chamber 18 cm long.…”

“…Table II clearly shows that platinized asbestos, cupric oxideferric oxide pellets, and powdered cupric oxide maintained at high temperatures (methods [20][21][22] provide the most efficient means of removing hydrocarbons from a continuous air flow system without creating the problems encountered with adsorbent traps. These catalysts depend upon a constant supply of 02 for regeneration.…”