Primary structure of the essential thiol peptide from the lactate dehydrogenase C subunit

Lactate dehydrogenase isozymes are inhibited when mercurial reagents are bound to cysteine-165 although no functional role is ascribed to this residue. Identical tryptic peptides containing this cysteine have been isolated from many LDH isozymes, including both A and B subunits. This report identifies an identical peptide from a third subunit type, C, of mouse. The rigorous conservation of this sequence implies an important functional role for this region of the molecule.