Evolution of aldehyde reductase: an immunological approach to the relatedness of aldehyde reductase from different species.

Antisera to aldehyde reductase from fruit-fly (Drosophila melanogaster) and chicken were cross-reacted with aldehyde reductase from several species of insects and birds using the technique of microcomplement fixation. Large differences in immunological distances are evident between species of the Class Insecta and of the Class Aves indicating considerable differences in the amino acid sequences of the aldehyde reductase of these species. Immunological distances for aldehyde reductase between pairs of insect species or bird species when plotted against the immunological distances for transferrin, albumin, lysozyme and alpha-glycerophosphate dehydrogenase for the same pairs of species gave a linear relationship in each case. From these relationships the rate of evolution of aldehyde reductase in terms of a unit evolutionary period (UEP) was calculated to be 12 which agreed favorably with the value previously obtained from compositional comparisons. A UEP of 12 is approximately half that of lactate dehydrogenase and shows that aldehyde reductase is evolving at twice the rate of glycolytic enzymes. This may indicate a relatively non-essential metabolism role for the enzyme.