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Delta Bilirubin: The Fourth Fraction of Bile Pigments in Human Serum
Author(s) -
Wu T.W.
Publication year - 1983
Publication title -
israel journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.908
H-Index - 54
eISSN - 1869-5868
pISSN - 0021-2148
DOI - 10.1002/ijch.198300034
Subject(s) - chemistry , bile pigments , bilirubin , pigment , albumin , diazo , human serum albumin , tetrapyrrole , amide , covalent bond , biochemistry , amine gas treating , bovine serum albumin , stereochemistry , organic chemistry , enzyme , medicine
Delta bilirubin is a strong, possibly covalent complex between bilirubin and an albumin‐like protein, found in the serum of most jaundiced adults. The bili‐albumin complex reacts directly diazo‐positive. An examination of its azo pigments indicates that only one half of the tetrapyrrole is linked to the protein, presumably via an amide bond formed between a propionic acid side chain of bilirubin and an amine group (e.g., ϵ‐NH 2 of a lysine) in the albumin backbone; the other (distal) propionic acid chain is largely unesterified. Preliminary analyses of the peptides generated by chemical or enzymic cleavage of the delta fraction suggest a bilirubin bonding region within positions 128–297 of albumin and another involving positions 298–585. Thus, delta bilirubin may represent the first true human biliprotein. The implications of this biliprotein in both the fundamental and applied aspects of bile pigment research are discussed.