Abstract
The formation of zinc protoporphyrin IX (ZPP) in porcine heart extract was investigated by visible absorption and fluorescent spectral analysis. Characteristic absorption peaks of ZPP were observed at 417, 546, and 584nm after anaerobic incubation of the extract with metmyoglobin and ZnCl2 in the dark at 30°C for 72h. In the fluorescent spectra (excitation : 410nm), a strong peak due to ZPP was obtained at 589nm. The time-course study showed that ZPP formation greatly increased after a lag period, during which metmyoglobin was reduced. ZPP formation was significantly facilitated by the use of oxymyoglobin. Zinc chelatase activity in the extract was estimated as 138mU/mL-extract and its specific activity was 2.95mU/mg-protein. The difference in activities with aerobic and anaerobic incubation was not significant. Measurements at pH 5.5-7.0 showed that activities were higher at lower pH. The activity of zinc chelatase was stimulated by the presence of ATP, and the highest activity was obtained at an ATP concentration of 2.5mg/mL.
