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UNIQef2ddd11b1dc5208-partinfo-00000000-QINU UNIQef2ddd11b1dc5208-partinfo-00000001-QINU

Background

[[Image:T--HFLS_H2Z_Hangzhou--img_enzyme_nor1.png]

Nitrous oxide reductase's tertiary structure

This enzyme catalyzes the reduction of nitrous oxide(N2O) to nitrogen(N2) and oxygen(O2). The enzyme comes from Agrobacterium tumefaciens. The enzyme contains two copper center, namely CuA and Cuz, which can transfer the electron.

Assay Method

We prepared a standard measuring mixture(2ml) consisting of 50mM Tris-HCL(pH9), 0.5mM methyl viologen, a proper amount of NosZ and 1mM sodium dithionite and 160uL of nitrous oxide solution.

Methyl viologen and sodium dithionite will go on to react and form a blue intermediate product, with a relatively stable absorbance at 600nm. The blue intermediate product serves as an electron donor for the reduction process of nitrous oxide. Therefore, as the reaction goes on, the blue substance starts to lose electrons and its color dims, resulting in a lower 600nm absorbance. Thus, by directly measuring the change of 600nm absorbance of the system, we are able to track the processing of the reaction.

Conclution

We delightedly found out that for just 900 seconds, the abs600 value of the color reagent dropped 32%. This represented nearly all the substrates had been converted to products in an extremely rapid rate: much more rapid than nitrite reductase.

And even though we cannot make the statement which among nosZ and NOR has a faster reactivity rate, we do know the fact that both enzymes react in a much faster rate than NiR.