Quantitative enzyme activity determination with zeptomole sensitivity by microfluidic gradient-gel zymography

Area of Science:

• Biochemistry
• Analytical Chemistry
• Biotechnology

Background:

• Zymography is crucial for enzyme analysis but often lacks sensitivity and quantitative kinetic data.
• Automated platforms can enhance throughput and precision in biochemical assays.

Purpose of the Study:

• To develop a sensitive, automated microfluidic zymography technique for comprehensive enzyme characterization.
• To demonstrate the utility of this method for analyzing enzyme molecular weight, amount, and kinetics (k(cat), K(m)).

Main Methods:

• Developed a two-step pore-limit electrophoresis with enzyme assay (PLENZ) in a microfluidic chip with a polyacrylamide gradient gel.
• Utilized pore-limit electrophoresis (PLE) for protein sizing and pseudoimmobilization, followed by substrate electrophoresis for activity assay.
• Employed fluorescence detection to quantify enzyme activity and determine kinetic parameters.

Main Results:

• Achieved a detection limit of 5 zmol (approx. 3,000 molecules) for Calf Intestinal Alkaline Phosphatase (CIP).
• Successfully demonstrated quantitative kinetic analysis (k(cat), K(m)) for CIP, revealing diffusional limitations.
• Showcased the method's versatility with Horseradish Peroxidase (HRP) and its applicability to dilute protein mixtures.

Conclusions:

• PLENZ provides a rapid, sensitive, and quantitative platform for enzyme functional analysis in complex samples.
• This technique has significant potential for applications in drug discovery, clinical diagnostics, and biocatalyst engineering.
• Physical pseudoimmobilization in PLENZ preserves enzyme turnover rate while allowing kinetic studies.