Biliverdin

Biliverdin is a green pigment formed as a byproduct of heme breakdown. It consists of four linearly connected pyrrole rings (a tetrapyrrole). Biliverdin is formed when a heme prosthetic group is cleaved at its α-methine bridge. The resulting water-soluble biliverdin (C₃₃H₃₄N₄O₆) is then converted to bilirubin (C₃₃H₃₆N₄O₆) by biliverdin reductase in macrophages of the reticuloendothelial system. The changing color of a bruise from deep purple to yellow over time is a graphical indicator of this reaction.

Biliverdin is also present in the bile juice which is secreted by the liver and also imparts color to the bile juice.

The green-blooded skinks of the genus Prasinohaema possess such high (and would otherwise be toxic) levels of biliverdin in their blood that their tissues are colored a bright green.

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Tetrapyrroles