Myoglobiini

Myoglobiini, known in English as myoglobin, is a small heme-containing protein expressed in muscle tissue. It is a monomeric globin with a single polypeptide chain of about 153 amino acids and a molecular weight of roughly 17 kilodaltons. The protein folds into the characteristic globin structure and contains a heme prosthetic group with iron in the ferrous state that reversibly binds a molecule of oxygen.

In skeletal and cardiac muscles, myoglobin serves as an oxygen carrier and storage. It binds oxygen with a high affinity and releases it when mitochondrial respiration increases during muscular activity, thereby facilitating oxygen diffusion to the working mitochondria. Myoglobin acts as an oxygen reservoir that helps sustain aerobic metabolism during early stages of increased demand. Because it is monomeric, its oxygen-binding curve is hyperbolic rather than sigmoidal, reflecting lack of cooperative binding.

Myoglobin expression is highest in oxidative muscle fibers (slow-twitch, type I) and to a lesser extent in glycolytic fibers (fast-twitch, type II). Levels can vary with species, age, training, and environmental conditions such as altitude.

Clinically, myoglobin can be released into the bloodstream after muscle injury and serves as an early but non-specific biomarker for muscle damage, including myocardial infarction and rhabdomyolysis. Serum or plasma myoglobin rises within hours after injury, peaks within a day or two, and is cleared by the kidneys; elevated levels can lead to pigmented urine.

In meat science, myoglobin content influences meat color, with higher levels giving a redder appearance.