Determination of Total Lactate
Dehydrogenase Activity in Serum Sample^32
32.1 Theory
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 containsfive isoenzymes (LDH1,
LDH2, LDH3, LDH4, and LDH5). These isoenzymes can be separated by electro-
phoresis. 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).
32.2 Specimen Requirements
Serum/plasma (heparin) is the preferred sample. Store at room temperature, do not
refrigerate or freeze, and sample should be free from any clot.
32.3 Principle........................................
LDH is an oxidoreductase enzyme that catalyzes the reversible oxidation of lactate to
pyruvate using NAD+as hydrogen acceptor. The equilibrium favors the conversion
of pyruvate to lactate at pH 7.4–7.8. The decrease in absorbance at 340 nm is directly
proportional to LDH activity.
#Springer Nature Singapore Pte Ltd. 2018
V. Kumar, K. D. Gill,Basic Concepts in Clinical Biochemistry: A Practical Guide,
https://doi.org/10.1007/978-981-10-8186-6_32
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