GLYCERALDEHYDE-3-PHOSPHATE DEHYDROGENASE IS AN ENZYME-CRYSTALLIN IN DIURNAL GECKOS OF THE GENUS PHELSUMA

Lenses from diurnal geckos, Phelsuma barbouri, Phelsuma madagascariens is grandis and Phelsuma serraticauda contain a prominent 37 kDa polype ptide (pi-crystallin) that is not present in lenses from the nocturnal geckos, Gekko gekko, Hemidactylus garnoti, Tarentola annularis, and U roplatus henkeli. This protein was partially purified from P. serratic auda and was identified as glyceraldehyde 3-phosphate dehydrogenase (G APD). The GAPDs, which constitute 14-24% of the lens soluble protein i n the diurnal species, were highly active. The presence of this enzyme in the lenses of diurnal, but not nocturnal, geckos supports the hypo thesis that the oxido-reductases found as enzyme-crystallins may funct ion in providing protection against the increased oxidative stress to which diurnal species are exposed. These findings strongly support the concept that the recruitment of enzyme-crystallins is a selective res ponse to changes in the visual environment.