title: Structural relatedness of mouse lactate dehydrogenase isozymes, A4 (muscle), B4 (heart), and C4 (testis).
abstract: Three homotetrameric lactate dehydrogenase isozymes, LDH-M(A4), LDH-H(B4), and LDH-X(C4), from DBA/2J mice have been purified by affinity chromatography.  The amino acid compositions of the subunits A,B, and C, based on a molecular weight of 36,000, have been determined.  The compositional relatedness of these isozymes indicates that subunits A (muscle) and B (heart) are more closely related to each other than to subunit C (testis).  Tryptic peptide maps and amino acid compositions of some active site peptides apear to confirm the compositional relatedness among these isozymes.  The sequence of the loop region of mouse C subunit seems to be markedly different from all known A and B sequences, and the structural and functional implications are discussed.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D000818:Animals; D004591:Electrophoresis, Polyacrylamide Gel; D007527:Isoenzymes / Q000032:analysis; D007770:L-Lactate Dehydrogenase / Q000032:analysis; D008297:Male; D051379:Mice; D008811:Mice, Inbred DBA / Q000235:genetics; D008970:Molecular Weight; D009132:Muscles / Q000201:enzymology; D009206:Myocardium / Q000201:enzymology; D011487:Protein Conformation; D013737:Testis / Q000201:enzymology
chemical_list: D000596:Amino Acids; D007527:Isoenzymes; D007770:L-Lactate Dehydrogenase