An inhibitive determination method for heavy metals using bromelain, a cysteine protease

Area of Science:

• Biochemistry
• Analytical Chemistry
• Environmental Science

Background:

• Proteases like bromelain are crucial enzymes in biological systems.
• Heavy metal contamination poses significant environmental and health risks.
• Existing heavy metal detection assays have limitations in sensitivity and scope.

Purpose of the Study:

• To develop a novel, sensitive assay for detecting heavy metal ions using bromelain.
• To evaluate the efficacy of the bromelain-based assay for quantifying mercury (Hg2+) and copper (Cu2+).
• To compare the sensitivity of the new assay with existing heavy metal detection methods.

Main Methods:

• A bromelain protease assay was established using casein as a substrate.
• Coomassie dye was employed to visually track the completion of casein hydrolysis.
• Assay conditions were optimized by excluding sulfhydryl protective agents and ethylenediaminetetraacetic acid (EDTA) to enhance sensitivity.
• The inhibition of bromelain activity by varying concentrations of Hg2+ and Cu2+ was measured.

Main Results:

• The bromelain assay effectively detects the presence of Hg2+ and Cu2+ through a colorimetric change (blue in presence of metals, brown when absent).
• Exclusion of specific agents significantly increased the assay's sensitivity to heavy metals.
• The assay demonstrated high sensitivity with an IC50 of 0.15 mg L(-1) for Hg2+ and 0.23 mg L(-1) for Cu2+.
• The IC50 values for both Hg2+ and Cu2+ were found to be lower than those reported for several other established assays.

Conclusions:

• The developed bromelain-based assay provides a sensitive and effective method for detecting heavy metals like Hg2+ and Cu2+.
• This assay shows improved sensitivity compared to existing methods, making it a valuable tool for environmental monitoring.
• The assay's simplicity and sensitivity offer a promising alternative for routine heavy metal analysis.