Myoglobin is a protein that stores and distributes oxygen in mammalian cells (mainly muscle cells). It is composed of a polypeptide chain and a prosthetic heme, with a relative molecular weight of 16700 and 153 amino acid residues. Myoglobin, which is called globulin after removing the accessory group of heme, has obvious homology in amino acid sequence with the subunits of hemoglobin (A-globin chain and P-globin chain), and their conformation and function are also very similar.
Myoglobin is a binding protein composed of a peptide chain and a heme prosthetic group. It is a protein that stores oxygen in muscle, and its oxygen saturation curve is hyperbolic. Myoglobin is found in muscle and is particularly abundant in the heart muscle. The tertiary structure of sperm whale myoglobin was elucidated by Kendrew in 1960 using X-ray diffraction, the first described tertiary structure of a protein in the world. Because the tertiary structure is directly related to the biological function of protein, and the analysis of tertiary structure is very difficult, so this work has been highly evaluated in the academic community.
Serum myoglobin can be used as the most sensitive indicator in the early diagnosis of acute myocardial infarction (AMI). But the specificity is poor, skeletal muscle injury, trauma, renal failure and other diseases, can lead to its elevation. Although positive myoglobin in cardiovascular test cannot confirm the diagnosis of AMI, it can be used as an important indicator to exclude the diagnosis of AMI in the early stage. If myoglobin is negative, myocardial infarction can be basically excluded, and it can also be used for the diagnosis of re-infarction. In combination with clinical practice, if myoglobin is re-elevated, it should be considered as re-infarction or infarction extension.
Increased myoglobin in cardiovascular tests is seen in the early stages of acute myocardial infarction, acute muscle injury, muscular dystrophy, muscular atrophy, polymyositis, acute or chronic renal failure, severe congestive heart failure, and prolonged shock. It can be increased 1.5h after myocardial infarction, but returns to normal within 1 to 2 days.
1. Increased myoglobin levels in cardiovascular tests: hypothyroidism, hyperaldosteronemia, renal insufficiency, malignant hyperfever and after strenuous exercise, etc.
2. Cardiovascular test myoglobinuria increased: porphyria, hemoglobinuria, hematuria, etc.
3. Cardiovascular test myoglobin increased in blood and urine: seen in acute myocardial infarction, angina pectoris, cardiogenic shock, cardiomyopathy, muscle diseases (progressive muscular dystrophy, polymyositis, myasthenia gravis), etc.