Multiple forms of lactate dehydrogenase in the cod,Gadus morhua L.

Five types of subunits are postulated to explain the lactate dehydrogenase zymogram patterns of cod tissues. The subunits designated A, B, and C occur predominantly in white skeletal muscle, heart, and liver tissues, respectively. The D subunit is found almost exclusively in the retina. Activity of the E subunit is found in most tissues but does not appear to be predominant in any one tissue. The A subunits are most susceptible to heat treatment. The B subunits are the least reactive when AcPyAD, an NAD analogue, is used in place of NAD. Subbands may be produced in incubating heart or muscle extracts with pyloric caeca extract or with trypsin or chymotrypsin. Subbands normally appearing in tissues zymograms may represent partially synthesized or partially degraded active LDH tetramers normally present in a metabolizing tissue. In a sampling of three Canadian and one European cod populations, four forms of the heart subunit were found. They are designated B, B, B, and B. Allele frequencies of the heart types for each population sample are compared.