S.F. Yang

Biosynthesis of ethylene. Ethylene formation from methional by horseradish peroxidase.

Abstract Ethylene is rapidly formed from methional by horseradish peroxidase, Mn+, SO32−, and a specific phenol, or by horseradish peroxidase, SO32−, catalytical amounts of hydrogen peroxide, and a specific phenol. The active phenols include some monohydric phenols and resorcinol. Ethylene formation is inhibited by o-dihydric phenols, Cu++, or metal chelators. Ethylene formation accompanies the aerobic oxidation of sulfite during the reactions, and those inhibitors which inhibit ethylene formation also inhibit the enzymic oxidation of sulfite. A mechanism accounting for the formation of ethylene and the physiological significance of this reaction in relation to the biosynthesis of ethylene in plants is discussed.

The biogenesis of ethylene in Penicillium digitatum

Abstract The origin of ethylene in Penicillium digitatum has been shown to be intimately associated with the Krebs cycle. 2-Ketoglutaric acid and glutamic acid are the most efficient precursors of ethylene, which is derived from carbons 3 and 4 of these substrates as a unit. However, which of these is the immediate precursor has not been established. Since 2-ketoglutaric acid is a very efficient precursor and succinic acid is an inefficient one, 2-ketoglutaric acid must be the branching point at which the pathway of ethylene biosynthesis leads away from the Krebs cycle. This conclusion is in full agreement with the following observations: Three of the four hydrogen atoms of the ethylene molecule were derived from protons of the medium; C-2 but not C-1 of acetate was incorporated into ethylene; and [2,3- 14 C]succinic acid but not [2,3- 3 H]succinic acid was incorporated.

Conversion of 5′-methylthioadenosine to methionine by apple tissue

Abstract Conversion of 5′-methylthioadenosine to methionine in apple tissue is demonstrated and discussed in relation to ethylene biosynthesis.

Ethylene formation from α-keto-γ-methylthiobutyrate by tomato fruit extracts

Abstract Cell-free extracts prepared from tomato fruits ( Lycopersicon esculentum Mill.) were not capable of catalyzing ethylene production from α-keto-γ-methylthiobutyrate, in the presence of Mn 2+ , sulfite, and phenol, until an endogenous heat-stable and dializable inhibitor was removed. After its removal, the enzyme-catalyzed formation of ethylene was readily demonstrated. Many of the properties of this tomato enzyme system relevant to ethylene production were found to be similar to those of the horse-radish peroxidase system.

Formation of ethionine from homocysteine and of S-methylmethionine from methionine in apple tissue

Abstract Conversion of l -homocysteine into ethionine and of methionine into S -methylcysteine in apple tissues is demonstrated.

The effect of ethylene on the development of phenylalanine ammonia-lyase in potato tuber disks

Summary PAL activity in potato tuber disks was markedly increased during the course of incubation. The amounts of ethylene from the disks were very low. Removal of ethylene from the disks slightly stimulated the increase in PAL activity while the addition of ethylene suppressed it. These results are in contrast with other system in which the development of PAL was greatly stimulated by ethylene.