A universal assay for screening expression libraries for carbohydrases

Area of Science:

• Biochemistry
• Enzymology
• Molecular Biology

Background:

• Existing assays for carbohydrases have limitations, failing to detect enzymes with incompatible substrates.
• Carbohydrases universally increase reducing ends during substrate degradation, a common property exploitable for detection.

Purpose of the Study:

• To explore the utility of the bicinchoninic acid (BCA) reducing value assay for detecting all types of carbohydrases.
• To screen a cDNA library of Aspergillus tubigensis for xylogalacturonan-degrading enzymes using the BCA assay.

Main Methods:

• Utilized the bicinchoninic acid (BCA) reducing value assay, a sensitive method for detecting increases in reducing ends.
• Screened a Kluyveromyces lactis expression library of Aspergillus tubigensis using the BCA assay and a xylogalacturonan substrate.
• Implemented specific precautions to mitigate high background absorbances from culture medium, proteins, and substrate.

Main Results:

• The BCA assay proved effective in detecting carbohydrases, including exo- and endo-acting enzymes simultaneously.
• Successfully identified three clones from the Aspergillus tubigensis library that produce xylogalacturonase.
• Demonstrated that background interference in the BCA assay can be managed effectively.

Conclusions:

• The bicinchoninic acid (BCA) reducing value assay is a versatile and sensitive tool for detecting a wide range of carbohydrases.
• This method enables the simultaneous detection of both exo- and endo-acting carbohydrases, overcoming limitations of existing assays.
• The successful screening of the Aspergillus tubigensis library highlights the applicability of this assay for enzyme discovery.