Hemocyanin:
- Similar to hemoglobin founded in vertebrates.
- Found in arthropods (especially crustaceans) and many molluscs.
- In the form of metalloproteins containing two copper atoms that reversibly bind a single oxygen molecule (O2). (Makes the blood blue from Cu2+ ion)
- Colourless when deoxygenated. (The blood appears as grey-white to pale yellow, due to the tissue fluid.)
- Dark blue when oxygenated.
- Most hemocyanins bind with oxygen non-cooperatively and are roughly one-fourth as efficient as hemoglobin at transporting oxygen per amount of blood.
- In some hemocyanins of horseshoe crabs and some other species of arthropods, cooperative binding is observed, with Hill coefficients between 1.6-3. (Hemoglobin for comparison has a Hill coefficient of usually 2.8-3)
- In case of cooperative binding, hemocyanin was arranged in protein sub-complexes of 6 subunits (hexamer), each with one oxygen binding site.
- Binding of oxygen on one unit in the complex would increase the affinity of the neighboring units.
- Hemocyanin oxygen-binding profile is also affected by dissolve-salt ion levels and pH.
- Hemocyanin oxygen transportation is more efficient than hemoglobin oxygen transportation in case of an animal that live in the cold environments and low oxygen pressure condition. (where several important marine invertebrates such as shrimps, crabs lives)
ไม่มีความคิดเห็น:
แสดงความคิดเห็น