Team:Hong Kong JSS/Model

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Team:Hong Kong JSS/Model

Michaelis-Menten kinetic equation

Michaelis-Menten kinetic equation is commonly used to describe enzyme kinetics for reactions involving a one step chemical reaction regarding an enzyme and a substrate. Our project focuses on the degradation of aflatoxin by laccase and FDR-A through redox reaction, therefore the Michaelis-Menten kinetic equation suits the reaction conditions.

Michaelis-Menten kinetic equation

The Michaelis constant (Km) is defined to be the substrate concentration at which the reaction rate is half of maximum rate at standard temperature and pressure. Catalytic rate constant (kcat) is defined as the maximum number of chemical reactions converting substrate to product in standard time. Km and kcat of TVlac and FDR-A were identified by literature search. Km and kcat for FDR-A on aflatoxin were found to be 47μM and 63min-1 respectively (Taylor, 2010) . Though TVlac was well known to degrade aflatoxin, the kcat for such reaction cannot be found in literature. However, Km and kcat for TVlac on ABTS (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)) were identified and used for graph generation. (Km: 38μM; kcat: 446.7min-1)

Comparison table of Km and kcat of TVlac and FDR-A

Graphical comparison

Aflatoxin catalytic characteristics

In another research, the aflatoxin catalytic characteristics of TVlac and FDR-A homolog (Actinomycetales sp.) were identified by experimental assay. The reported aflatoxin catalytic rates for TVlac and FDR-A were 0.37μg h-1 mg-1 and 11mg h-1 mg-1 respectively.

Aflatoxin catalytic characteristics comparison table of TVlac and FDR-A (Actinomycetales sp.)

The graph shows that the time required for FDR-A undergo aflatoxin degradation is much less than TVlac.

As a result, FDR-A is more preferred to be used in our final product. It is because it requires less time to degrade aflatoxin.

Lyagin, I., & Efremenko, E. (2019). Enzymes for detoxification of various mycotoxins: Origins and mechanisms of catalytic action. Molecules, 24(13), 2362.

Taylor, M.C., Jackson, C.J., Tattersall, D.B., French, N., Peat, T.S., Newman, J., Briggs, L.J., Lapalikar, G.V., Campbell, P.M., Scott, C., Russell, R.J., Oakeshott, J.G., 2010. Identifica- tion and characterization of two families of F420H2-dependent reductases from Mycobacteria that catalyse aflatoxin degradation. Mol. Microbiol 78, 561–575.

Verheecke, C., Liboz, T., & Mathieu, F. (2016). Microbial degradation of aflatoxin B1: current status and future advances. International journal of food microbiology, 237, 1-9.

Wu, M. H., Lee, C. C., Hsiao, A. S., Yu, S. M., Wang, A. H. J., & Ho, T. H. D. (2018). Kinetic analysis and structural studies of a high‐efficiency laccase from Cerrena sp. RSD 1. FEBS Open bio, 8(8), 1230-1246.
Zeinvand-Lorestani, H., Sabzevari, O., Setayesh, N., Amini, M., Nili-Ahmadabadi, A., & Faramarzi, M. A. (2015). Comparative study of in vitro prooxidative properties and genotoxicity induced by aflatoxin B1 and its laccase-mediated detoxification products. Chemosphere, 135, 1-6.