Biglutaminyl-Biliverdin IX Alpha as a Heme Degradation Product in the Dengue Fever Insect-Vector Aedes aegypti

• Published in: Biochemistry (Easton) Vol. 46; no. 23; pp. 6822 - 6829
• Main Authors: Pereira, Luiza O. R, Oliveira, Pedro L, Almeida, Igor C, Paiva-Silva, Gabriela O
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 12-06-2007
• Subjects: Aedes - metabolism; Aedes aegypti; Animals; Bile Pigments - chemistry; Bile Pigments - isolation & purification; Biliverdine - analogs & derivatives; Biliverdine - chemistry; Biliverdine - metabolism; Dengue; Heme - metabolism; Insect Proteins - metabolism; Insect Vectors; Models, Molecular; Molecular Sequence Data; Pigments, Biological - chemistry; Pigments, Biological - isolation & purification; Pigments, Biological - metabolism; Rhodnius prolixus
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi700011d

Hemoglobin digestion in the midgut of hematophagous animals results in the release of its prosthetic group, heme, which is a pro-oxidant molecule. Heme enzymatic degradation is a protective mechanism that has been described in several organisms, including plants, bacteria, and mammals. This reaction is catalyzed by heme oxygenase and results in formation of carbon monoxide, ferrous ion, and biliverdin IXα. During digestion, a large amount of a green pigment is produced and secreted into the intestinal lumen of Aedes aegypti adult females. In the case of another blood-sucking insect, the kissing-bug Rhodnius prolixus, we have recently shown that heme degradation involves a complex pathway that generates dicysteinyl-biliverdin IX gamma. The light absorption spectrum of the Aedes purified pigment was similar to that of biliverdin, but its mobility on a reverse-phase chromatography column suggested a compound less hydrophobic than biliverdin IXα. Structural characterization by ESI-MS revealed that the mosquito pigment is the α isomer of biliverdin bound to two glutamine residues by an amide bond. This biglutaminyl-biliverdin is formed by oxidative cleavage of the heme porphyrin ring followed by two subsequent additions of glutamine residues to the biliverdin IXα. The role of this pathway in the adaptation of this insect vector to a blood-feeding habit is discussed.