Laccase activity tests and laccase inhibitors

Area of Science:

• Biochemistry
• Enzymology
• Mycology

Background:

• Laccase enzymes are crucial in various biotechnological applications.
• Sulfhydryl compounds are often investigated for their potential laccase inhibitory properties.
• Accurate enzyme inhibition assays are vital for understanding enzyme mechanisms and applications.

Purpose of the Study:

• To investigate the inhibitory effects of specific sulfhydryl organic compounds on Trametes versicolor laccase.
• To clarify previously reported inhibitory effects of these compounds on laccase activity.
• To evaluate the reliability of common enzyme assay substrates in the presence of these compounds.

Main Methods:

• Tested dithiothreitol, thioglycolic acid, cysteine, diethyldithiocarbamic acid, and sodium azide for laccase inhibition.
• Utilized two enzyme substrates: 2, 2'-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) and 2, 6-dimethoxyphenol.
• Analyzed potential non-enzymatic interactions and interference with reaction products.

Main Results:

• Only sodium azide demonstrated true laccase inhibition without interfering with the assay.
• Other tested sulfhydryl compounds did not significantly inhibit laccase activity.
• Observed underestimation of laccase activity due to non-enzymatic interactions and complex formation with ABTS.

Conclusions:

• Previously reported inhibition by sulfhydryl compounds is attributed to assay interference, not direct enzyme inhibition.
• Sodium azide is a reliable inhibitor for Trametes versicolor laccase.
• Careful selection of enzyme substrates and assay conditions is necessary when evaluating potential inhibitors.