bilirubin oxidase

{{infobox enzyme

| Name = bilirubin oxidase

| EC_number = 1.3.3.5

| CAS_number = 80619-01-8

| GO_code = 0047705

| image = MvBO_2xll_thumb.png

| width = 220px

| caption = Cartoon representation of the X-ray structure of bilirubin oxidase from Myrothecium verrucaria based on PDB accession code {{PDB link|2xll}}. The protein ribbon is rainbow colored with the N-terminus in blue and the C-terminus in red. The four copper atoms are shown as spheres and the glycans shown as sticks.

}}

In enzymology, a bilirubin oxidase, BOD or BOx, ({{EC number|1.3.3.5}}) is an enzyme encoded by a gene in various organisms that catalyzes the chemical reaction

:2 bilirubin + O₂ $\backslash rightleftharpoons$ 2 biliverdin + 2 H₂O

This enzyme belongs to the family of oxidoreductases, to be specific those acting on the CH-CH group of donor with oxygen as acceptor. The systematic name of this enzyme class is bilirubin:oxygen oxidoreductase. This enzyme is also called bilirubin oxidase M-1. This enzyme participates in porphyrin and chlorophyll metabolism. It is widely studied as a catalyst for oxygen reduction.{{cite journal | vauthors = Mano N, Edembe L | title = Bilirubin oxidases in bioelectrochemistry: features and recent findings | journal = Biosensors & Bioelectronics | volume = 50 | pages = 478–485 | date = December 2013 | pmid = 23911663 | doi = 10.1016/j.bios.2013.07.014 }}

Two structures of bilirubin oxidase from the ascomycete Myrothecium verrucaria have been deposited in the Protein Data Bank (accession codes {{PDB link|3abg}} and {{PDB link|2xll}}).{{cite journal | vauthors = Mizutani K, Toyoda M, Sagara K, Takahashi N, Sato A, Kamitaka Y, Tsujimura S, Nakanishi Y, Sugiura T, Yamaguchi S, Kano K, Mikami B | display-authors = 6 | title = X-ray analysis of bilirubin oxidase from Myrothecium verrucaria at 2.3 A resolution using a twinned crystal | journal = Acta Crystallographica. Section F, Structural Biology and Crystallization Communications | volume = 66 | issue = Pt 7 | pages = 765–770 | date = July 2010 | pmid = 20606269 | pmc = 2898457 | doi = 10.1107/S1744309110018828 }}{{cite journal | vauthors = Cracknell JA, McNamara TP, Lowe ED, Blanford CF | title = Bilirubin oxidase from Myrothecium verrucaria: X-ray determination of the complete crystal structure and a rational surface modification for enhanced electrocatalytic O2 reduction | journal = Dalton Transactions | volume = 40 | issue = 25 | pages = 6668–6675 | date = July 2011 | pmid = 21544308 | doi = 10.1039/c0dt01403f }}

The active site consists of four copper centers, reminiscent of laccase. These centers are classified as type I (cys, met, his, his), type II (3his), and two type III (2his).{{cite journal | vauthors = Jones SM, Solomon EI | title = Electron transfer and reaction mechanism of laccases | journal = Cellular and Molecular Life Sciences | volume = 72 | issue = 5 | pages = 869–883 | date = March 2015 | pmid = 25572295 | pmc = 4323859 | doi = 10.1007/s00018-014-1826-6 }} The latter two centers are arranged in a trinuclear copper cluster forming the active site for oxygen reduction.{{cite journal | vauthors = Mano N, de Poulpiquet A | title = O₂ Reduction in Enzymatic Biofuel Cells | journal = Chemical Reviews | volume = 118 | issue = 5 | pages = 2392–2468 | date = March 2018 | pmid = 28930449 | doi = 10.1021/acs.chemrev.7b00220 | url = https://hal.archives-ouvertes.fr/hal-01731291/file/P118-12485.pdf }} The type I copper center is the primary electron acceptor and the site for the reduction of bilirubin.