Bilirubin

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Contents 1 More Specific Terms 2 Introduction 3 More General Terms 4 Additional Terms 5 Internet Database 6 References

More Specific Terms

• bilirubin diglucuronide; conjugated bilirubin; direct bilirubin
• delta bilirubin

Introduction

• Bilirubin is a waste product of heme metabolism, produced largely in the spleen where senescent erythrocytes are phagocytosed. However, it is also produced in the brain where it may serve a constituent role as an antioxidant.

• Bilirubin is formed from heme by sequential actions of heme oxygease in association with cyt P450 reductase & bilirubin reductase.

*                     heme oxygenase 
*                   cyt P450 reductase 
* heme[Fe+2] + O2   ------------------>   biliverdin + CO + Fe+2 
* + NADPH + H+                            + NADP+  + H2O 
*                 biliverdin reductase 
*     biliverdin  -------------------->   bilirubin + NADP+ 
*   + NADPH + H+

• Biliverdin reductase rapidly reduces biliverdin to bilirubin.
• Bilirubin binds non-covalently to albumin (unconjugated bilirubin) for transport to the liver, where it is conjugated with glucuronic acid (conjugated bilirubin), then excreted in the bile. In certain conditions, bilirubin may also bind covalently to albumin to form delta-bilirubin.
• Bilirubin has the capacity to reduce 10,000 higher fold concentrations of H2O2 through the biliverdin reductase cycle.

More General Terms

• heme metabolite
• pigment

Additional Terms

• bilirubin conjugated in serum
• bilirubin in urine (Ictotest)
• bilirubin unconjugated in serum
• heme catabolism

Internet Database

PubChem: 250
PubChem: 5315454
PubChem: 457804
PubChem: 5280352
PubChem: 8235

References

1. Clinical Diagnosis & Management by Laboratory Methods, J.B. Henry (ed), W.B. Saunders Co., Philadelphia, PA. 1991, pg 233
2. Sedlak TW, Snyder SH. Messenger molecules and cell death: therapeutic implications. JAMA. 2006 Jan 4;295(1):81-9. PMID: [1]

bilirubin