SEQUENCE SIMILARITIES OF GLYCERALDEHYDE-3-PHOSPHATE DEHYDROGENASES, PHOSPHOGLYCERATE KINASES, AND PYRUVATE KINASES ARE SPECIES OPTIMAL TEMPERATURE-DEPENDENT

Data are presented that suggest enzyme sequence similarities among spe cies are not solely a function of their evolutionary relationship. It is demonstrated that sequence similarities of glyceraldehyde-3-phospha te dehydrogenases, phosphoglycerate kinases, and pyruvate kinases from yeast, bacteria, mammals and a bird possess a significant species opt imal thriving temperature dependence that crosses through conventional phylogenetic divisions. It is therefore suggested that species which are distantly related evolutionarily may possess some degree of enzyme sequence similarity if they happen to thrive at near the same optimal temperature; conversely, organisms which are closely related evolutio narily but function at radically different temperatures will possess a sequence dissimilarity that may mask the close relatedness.