Characterization of 1-aminocyclopropane-1-carboxylic acid oxidase from barley (Hordeum vulgare L.) seedlings and pine (Pinus sylvestris L.) needles

Biochemical characteristics of 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase extracted from barley (Hordeum vulgare L.) leaves and pine (Pinus sylvestris L.) needles were investigated. ACC oxidase from barley leaves was soluble while for complete recovery of ACC oxidase from pine needles addition of Triton X-100 to extraction medium was necessary. The enzyme required Fe²⁺, ascorbate and NaHCO₃ for maximum activity. A non- linear time course of ACC oxidase reaction indicated possible catalytic inactivation of the enzyme. The maximum activity was measured at pH 7.0-7.2 for ACC oxidase from both barley leaves and pine needles. The apparent K(m) for ACC was found to be 77 and 61 μM in the presence of 20 mM NaHCO₃, for barley and pine ACC oxidase, respectively. The presence of low molecular weight inhibitors in the crude extract from pine needles was found that were separated by a chromatography on Sephadex column. The first peak of a putative activity of ethylene formation eluted from Sephadex column during chromatography of pine needle extract appeared not to represent a native ACC oxidase.