Evaluation of the Ethylene Effect on Well Defined Copper Enzymes
Abstract: An indirect approach
in studying ethylene binding sites of copper enzymes was carried out since
ethylene pleitropic effect in plants and the general affinity of Cu(I)
complexes for ethylene suggest a possibility of ethylene binding to various
copper enzymes. For this purpose, superoxide dismutase (SOD) and tyrosinase
were evaluated using two different methods. H-NMR spectra of three different
conditions of SOD (native SOD; reduced SOD; and reduced SOD in the presence of
ethylene) were acquired at 25 °C. Activity of mushroom tyrosinase was monitored
in the absence of ethylene by evaluating the formation of dopachrome at 475 nm.
Three other assay systems were constructed the same way as the control, except
one of the reagents (enzyme, DL-DOPA, or sodium phosphate buffer) was each
saturated with ethylene prior to mixing all of reagents. Both systems behaved
unsatisfactorily for the purpose of evaluation. The coordinated ethylene
proton-NMR signal was obscured by the broad HOD signal, due to the partial
oxidation of Cu(I) SOD by trace oxygen. Nonetheless, the tyrosinase assay
results demonstrated that displacement of oxygen in the assay system by
ethylene did not account for the loss of activity. The observed ethylene effect
on tyrosinase activity, however, was minimal, since ethylene could produce
threshold physiological response at concentration of 6.5 x 10 -9 M.
Author: Megawati Santoso,
Harold M. Goff
Journal Code: jpkimiagg060002
