Home > Lactate dehydrogenase

1 Enzyme isoforms

Every LDH molecule consists of four subunits, where each subunit is either H each M (based on their electrophoretic properties.) There are, therefore, five LDH isotypes:

• LDH-1 (4H) - in the heart
• LDH-2 (3H1M) - in the reticuloendothelial system
• LDH-3 (2H2M) - in the lungs
• LDH-4 (1H3M) - in the kidneys
• LDH-5 (4M) - in the liver and striated muscle

Usually LDH-2 is the predominant form in the serum. An LDH-1 level higher than the LDH-2 level (a "flipped pattern"), suggests myocardial infarction (damage to heart tissues releases heart LDH, which is rich in LDH-1, into the bloodstream). The use of this pheonomenon to diagnose infarction has been largely superseded by the use of Troponin I or T measurement.

2 Genetics in Humans

The H and M subunits are encoded by two different genes:

• The M subunit is encoded by LDHA, located on chromosome2) Centromere. The point where the two chromatids touch, and where the microtubules attach. 3) Short arm. 4) Long arm. A chromosome is, minimally, a very long, continuous piece of DNA, which contains many genes, regulatory elements and other intervening n 11p15.4 ( OMIM [http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id= } }])
• The H subunit is encoded by LDHB, located on chromosome 12p12.2-p12.1 ( OMIM [http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id= } }])

Mutations of the M subunit have been linked to the rare disease exertional myoglobinuria (see OMIM article), and mutations of the H subunit have been described but do not appear to lead to disease.

3 Medical use

3.1 Hemolysis

In medicineSee drugs, medication, and pharmacology for substances that treat patients. This article is about medical practice. Medicine is a branch of health science concerned with restoring and maintaining health and wellness. Broadly, it is the practical science o, LDH is often used as a marker of tissue breakdown. As LDH is abundant in red blood cellRed blood cells are the most common type of blood cell and are the vertebrate body's principal means of delivering oxygen to body tissues via the blood. Red blood cells are also known as erythrocytes from Greek erythros for "red" and kytos for "hollow", ns, it can function as a marker for hemolysisHemolysis (alternative spelling haemolysis is the excessive breakdown of red blood cells. When this happens, it causes a form of anemia. Hemolysis is also an important factor in medical tests, as a blood sample may become hemolysed with prolonged storage,. A blood sample that has been handled incorrectly can show false-positively high levels of LDH due to erythrocyte damage.