The tentative amino acid sequencing of lactate dehydrogenase C4 by X-ray diffraction analysis.

A tentative amino acid sequence of mouse testicular lactate dehydrogenase C4 was deduced from an electron density map and comparison with five other known lactate dehydrogenase sequences. The amino acid composition determined by chemical analysis agrees reasonably well with the present results. Necessary changes in amino acids were largely conservative and confined to the external portions of the molecule. Residues in the Q and P subunit contact regions were particularly well conserved as were most internal residues. The minimum base change/codon was similar between the C and H isoenzymes and between the C and M isoenzymes.