Effects of Iron (II) (Fe2+) and Iron (III) (Fe3+) ions on the Activity and Stability Bromelain
Article
Figures
Metrics
Preview PDF
Reference
Related
Cited by
Materials
Abstract:
The effects of different concentrations of iron (II) (Fe2+) and iron (III) (Fe3+) on the activity of bromelain and the thermostability of bromelain at 60 ℃ were studied, and circular dichroism (CD) spectra were used to determine conformational changes of bromelain caused by Fe2+ and Fe3+. In addition, the iron ion removal effect of a method combining ethylenediaminetetraacetic acid disodium salt and ultrafiltration during the preparation of bromelain was preliminarily explored. The results showed that Fe2+ at a concentration range from 0 to 0.75 mmol/L improved the activity of bromelain, and the best Fe2+ concentration was found as 0.5 mmol/L. When the concentration of Fe2+ was higher than 0.75 mmol/L, the activity of the enzyme was inhibited, and the extent of inhibition was increased with increasing Fe2+ concentration. Fe3+ had an inhibitory effect on enzyme activity, and the extent of inhibition was proportional to the concentration of Fe3+. The inhibitory effect of Fe3+ on the enzyme was stronger than that of Fe2+. At 0.5 mmol/L, Fe2+ had a promoting effect on the thermostability of bromelain at 60 ℃ and extended the half-life of the enzyme. However, Fe3+ had an inhibitory effect on the thermostability of bromelain. When the concentrations of Fe2+ and Fe3+ were higher than 0.5 mmol/L, their inhibitory effects on the thermostability of bromelain increased with increasing ion concentration. According to CD spectra, the inhibitory effects of Fe2+ and Fe3+ on bromelain were reflected in a decrease in the contents of α-helices, a slight decrease in the contents of β-sheets and β-turns, and a significant increase in random coil contents. The method combining ethylenediaminetetraacetic acid disodium salt and ultrafiltration was effective for iron ion removal, with a reduction of iron content from 291.63 mg/kg to 142.99 mg/kg (dry weight), and the elimination rate of iron ion was 50.97%. Moreover, the enzyme activity increased from 597.27 U/mg to 808.52 U/mg, and the growth rate of activity was increased by 26.13%.
