Hemoproteins

Myoglobin (symbol Mb or MB) is an iron- and oxygen-binding protein found in the cardiac and skeletal muscle tissue of vertebrates in general and in almost all mammals. Myoglobin is distantly related to hemoglobin. Compared to hemoglobin, myoglobin has a higher affinity for oxygen and does not have cooperative binding with oxygen like hemoglobin does. Myoglobin consists of non-polar amino acids at the core of the globulin, where the heme group is non-covalently bounded with the surrounding polypeptide of myoglobin. In humans, myoglobin is found in the bloodstream only after muscle injury.

Catalase is a common enzyme found in nearly all living organisms exposed to oxygen (such as bacteria, plants, and animals) which catalyzes the decomposition of hydrogen peroxide to water and oxygen. It is a very important enzyme in protecting the cell from oxidative damage by reactive oxygen species (ROS). Catalase has one of the highest turnover numbers of all enzymes; one catalase molecule can convert millions of hydrogen peroxide molecules to water and oxygen each second.

thumb|right|Glutathione Peroxidase 1 ()

complex enzyme found in bacteria, archaea, and mitochondria of eukaryotes

thumbnail|right|The structure of cytochrome b5 reductase, the enzyme that converts methemoglobin to hemoglobin.

Myeloperoxidase (MPO) is a peroxidase enzyme that in humans is encoded by the MPO gene on chromosome 17. MPO is most abundantly expressed in neutrophils (a subtype of white blood cells), and produces hypohalous acids to carry out their antimicrobial activity, including hypochlorous acid, the sodium salt of which is the chemical in bleach. It is a lysosomal protein stored in azurophilic granules of the neutrophil and released into the extracellular space during degranulation. Neutrophil myeloperoxidase has a heme pigment, which causes its green color in secretions rich in neutrophils, such as m

thumb|upright=1.35|Leghemoglobin A from a soybean (PDB: 1BIN)

Neuroglobin is a member of the vertebrate globin family involved in cellular oxygen homeostasis and reactive oxygen/nitrogen scavenging. It is an intracellular hemoprotein expressed in the central and peripheral nervous system, cerebrospinal fluid, retina and endocrine tissues. Neuroglobin is a monomer that reversibly binds oxygen with an affinity higher than that of hemoglobin. It also increases oxygen availability to brain tissue and provides protection under hypoxic or ischemic conditions, potentially limiting brain damage. Neuroglobin were in the past found only in vertebrate neurons, but

thumb|420 px|Binding of oxygen to a heme prosthetic group, which would be part of a hemoprotein.

Deoxygenated blood increases the capacity for carbon dioxide transport

class of enzymes

Cytoglobin is the protein product of CYGB, a human and mammalian gene.

Complex that transfers electrons from reduced plastoquinone to oxidized plastocyanin and translocates protons from the stroma to the lumen

thumb|Heme in chlorocruorin, the source of its unique green color. Erythrocruorin (from Greek eruthros "red" + Latin cruor "blood"), and the similar chlorocruorin (from Greek khlōros "green" + Latin cruor "blood"), are large oxygen-carrying hemeprotein complexes, which have a molecular mass greater than 3.5 million daltons. Both are sometimes called giant hemoglobin or hexagonal bilayer haemoglobin. They are found in many annelids and arthropods (including some insects).

REDIRECT Erythrocruorin

class of enzymes

Metmyoglobin is the oxidized form of the oxygen-carrying hemeprotein myoglobin. Metmyoglobin is the cause of the characteristic brown colouration of meat that occurs as it ages.