Different segment similarities in long-chain dehydrogenases.

Long-chain dehydrogenases were scrutinized for common patterns. Overall molecular similarities are not discerned, in contrast to the situation for several short-chain and medium-chain dehydrogenases, but coenzyme-binding segments are discernible. Species variants of glucose-6-phosphate dehydrogenase reveal about 20% strictly conserved residues, grouped into three segments and supporting assignments of sites for coenzyme-binding and catalysis. Glycine is overrepresented among the residues conserved, typical of distantly related proteins. Two of the enzymes within the pentose phosphate pathway reveal a distant similarity of interest for further evaluation, between a C-terminal 178-residue segment of glucose-6-phosphate dehydrogenase and the N-terminal part of 6-phosphogluconate dehydrogenase.