Determination of L-lactate binding stoichiometry and differences in allosteric interactions of structurally distinct homohexamers from Panulirus interruptus hemocyanin.

The role of structurally distinct subunits from the hemocyanin of Panulirus interruptus was investigated by the analysis of the oxygen-binding properties of reassembled homohexamers. Homohexamers reassembled from subunits a and b exhibited cooperative oxygen binding, whereas subunit c did not. The oxygen affinity of homohexamers from subunits b and c was specifically increased by the addition of L-lactate, whereas that of subunit a was not. Both native hexamers and the homohexamers from subunit b have approximately one oxygen-linked lactate binding site per hexamer.