Somatic and sperm-specific isoenzymes of glyceraldehyde-3-phosphate dehydrogenase: comparative analysis of primary...

The elucidation of the interdependence between structural features and functions of somatic and sperm-specific isoenzymes of glyceraldehyde-3-phosphate dehydrogenase (GAPD and GAPDS, respectively) was the goal of comparative analysis of their primary structures. GAPDS was shown to lack the sequence similar to the atypical nuclear export signal motif (NES) of the somatic isoenzyme GAPD. This finding is confirmed by experimental data on the absence of interaction between GAPDS and antibodies 6C5 recognizing the NES motif in the sequence of GAPD. The lack of NES correlates with functional peculiarities of the sperm-specific enzyme that is tightly bound to the fibrous sheath of the sperm flagellum. The sequences of the two isoenzymes were examined for the short motifs that might participate in apoptosis, endocytosis, and DNA repair. Sites of phosphorylation by different protein kinases have been revealed in both isoenzymes, and their characteristic features are discussed. These observations can serve as the basis for subsequent search for new ways of regulating the two isoenzymes.