Determination of Total Lactate Dehydrogenase Activity in Serum Sample
Lactate dehydrogenase (LDH) is an enzyme involved in glucose metabolism. LDH is widely distributed in all cells but especially abundant in cardiac and skeletal muscles, liver, kidney, and red blood cells. LDH contains five isoenzymes (LDH1, LDH2, LDH3, LDH4, and LDH5). These isoenzymes can be separated by electrophoresis. LDH1 has more positive charge and hence fastest in electrophoresis mobility, while LDH5 is slowest in mobility. LDH is an oligomeric enzyme made up of four polypeptide subunits. Two types of subunits M (for muscle) and H (for heart) are produced by different genes. LDH1 is predominantly found in the heart, while LDH5 occurs in skeletal muscles. Total LDH activity is measured as combined activity of all isoenzymes in plasma (LDH1 and LDH2 are predominant in plasma than LDH3, LDH4, and LDH5 which are present only in small amounts).