Enzymic oxidation of unconjugated bilirubin by rat liver

Abstract

The presence of the enzyme bilirubin oxidase, which degrades bilirubin in vitro, was demonstrated in the liver. Subcellular-fractionation experiments indicate that bilirubin oxidase is located in both the inner and outer membranes of the mitochondria. The mean rate of the reaction is 1.57 +/- 0.38 (S.D.) nmol of bilirubin degraded/min per mg of mitochondrial protein (munits/mg of protein). With respect to the overall breakdown of bilirubin, the enzyme has a Km' of 136 microM-bilirubin and a Vmax.' of 9.13 munits/mg of protein. Its activity is influenced by the ionic strength of the media and is inhibited by KCN, thiol reagents, NADH and albumin. The enzyme is aerobic, and between 1 and 1.5 mol of O2 are consumed per mol of bilirubin degraded. The products of the reaction include propentdyopents. The hepatic bilirubin oxidase activity of the jaundiced Gunn-rat liver is not significantly different from that of the Sprague-Dawley rat, and it is not induced by beta-naphthoflavone.

Bilirubin Oxidase Activity of Bacillus subtilis CotA

“…Bilirubin oxidase (BOD; EC 1.3.3.5) catalyzes the oxidation of bilirubin to biliverdin (2) and is used clinically to determine the levels of total and conjugated bilirubin in serum (3,12,14). It is distributed mainly in fungi, and BODs from Myrothecium verrucaria (20) and Trachyderma tsunodae K-2593 (6) have been purified and characterized.…”

2,3,7,8‐Tetrachlorodibenzo‐p‐dioxin (TCDD) Increases Bilirubin Formation but Hampers Quantitative Hepatic Conversion of Biliverdin to Bilirubin in Rats with Wild‐Type AH Receptor

“…In addition to the induction of HO-1 (see above), other connections are possible. For example, some bilirubin might be oxidized to biliverdin by hepatic bilirubin oxidase [34][35][36], whereas non-enzymatic oxidation of bilirubin to biliverdin or bilirubin conjugates to respective biliverdin conjugates by reactive oxygen species does neither seem probable in the light of the current correlation analysis, nor according to the literature [37]. On the other hand, in brain, decreased catalytic activity of BVR-A due to oxidative/nitrosative stressinduced modifications has been observed [38].…”

“…Ahr wt , aryl hydrocarbon receptor, wild‐type; BRO , bilirubin oxidase; BVR ‐A, biliverdin reductase A; HO ‐1, haem oxygenase‐1; MRP 2, multi‐drug resistance protein 2; UGT 1A1, bilirubin uridine diphosphate ( UDP )‐glucuronosyltransferase. Presence of hepatic BRO has been shown in mice (cytochrome P450 2A5) , human beings (cytochrome P450 2A6) and rats ; however, it does not seem to play a major role in TCDD ‐induced biliverdin accumulation (see text for details). *acutely toxic dose.…”

A Thermostable Bilirubin-Oxidizing Enzyme from Activated Sludge Isolated by a Metagenomic Approach

“…The metagenomics of activated sludge from a coke plant were used to isolate a gene encoding a biocatalytic enzyme (21). BOD catalyzes the oxidation of bilirubin to biliverdin (5) and is used clinically to measure the levels of total and conjugated bilirubin in serum (7, 23, 33). BopA is a thermostable BOD that exhibits markedly higher thermostability than that reported for laccases; BopA appears to be the most thermostable BOD identified to date.…”