Preliminary characterizations of esterase and cholinesterase activities in etiolated barley, rice, and maize seedlings

This study represents preliminary characterizations of esterase and cholinesterase activities in barley (Hordeum vulgare cv Himalaya), in rice (Oryza sativa japonica cv Calrose 76), and in maize (Zea mays cv Pioneer 3145). The activities were partially purified by 30% to 90% ammonium sulfate fractionation and Sephadex G-200 column chromatography. Characterizations of activities were attempted by observing the effects of pH, temperature, dicationic metals, and cholinesterase inhibitors.

Barley and maize were found to exhibit relatively strong esterase and cholinesterase activities and rice was found to have a strong esterase activity but lacks cholinesterase activity. Activities from all three sources had pH optima between 7.0 and 8.0 and were temperature stable to at least 30 C. Inhibition by metal ions varied greatly depending on source and activity while only maize activities exhibited sensitivity to inhibitors. Based on this research, the activities from these sources do not exhibit cholinesterase or acetylcholinesterase activities by the criteria used to describe similar activities in animal systems.

Little information is available concerning the metabolic roles of the esterase activities and their substrates in vivo. Conjectures related to possible functions of the esterase system in the whole plant system are considered.