Enzymic oxidation of unconjugated bilirubin by rat liver.
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.
D000818:Animals; D001571:Benzoflavones / Q000494:pharmacology; D001663:Bilirubin / Q000378:metabolism*; D001664:Biliverdine / Q000378:metabolism; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D008297:Male; D008930:Mitochondria, Liver / Q000201:enzymology; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D044925:Oxidoreductases Acting on CH-CH Group Donors; D051381:Rats; D011911:Rats, Gunn; D011919:Rats, Inbred Strains; D013347:Subcellular Fractions / Q000201:enzymology; D019324:beta-Naphthoflavone
D001571:Benzoflavones; D019324:beta-Naphthoflavone; D010088:Oxidoreductases; D044925:Oxidoreductases Acting on CH-CH Group Donors; C042401:bilirubin oxidase; D001664:Biliverdine; D001663:Bilirubin