A novel ethylene-forming enzyme that catalyses the formation of ethylene from 2-oxoglutarate was purified from a cell-free extract of pv. PK2. It was purified about 2800-fold with an overall yield of 53% to a single band of protein after SDS-PAGE. The purified enzyme had a specific activity of 660 nmol ethylene min (mg protein). The molecular mass of the enzyme was approximately 36 kDa by gel filtration and 42 kDa by SDS-PAGE. The isoelectric point and optimum pH were 5.9 and ca. 7.0-7.5 respectively. There was no homology between the N-terminal amino acid sequence of the ethylene-forming enzyme of pv. PK2 and the sequence of the ethylene-forming enzyme of the fungus IFO 9372. However, the two enzymes have the following properties in common. The presence of 2-oxoglutarate, l-arginine, Fe and oxygen is essential for the enzymic reaction. The enzymes are highly specific for 2-oxoglutarate as substrate and L-arginine as cofactor. EDTA, Tiron, DTNB [5,5′-dithio-bis(2-nitrobenzoate)] and hydrogen peroxide are all effective inhibitors.


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