Isozyme distribution of eleven enzymes and their loci in Australian lungfish, Neoceratodus forsten (Osteichthyes, Dipnoi)

Abstract

Eleven enzymes were analysed in seven tissues (heart, muscle, liver, kidney, gills, gut, and lung) of the Australian lungfish with the aim of identifying the distribution in an extant sarcopterygian fish and of comparing this distribution to patterns previously described in actinopterygian fishes and other vertebrates. Some enzymes (G6PDH, GPI, LDH, MDH, and SOD) were found to be present in all the tissues studied, while the others were found to be tissue specific. Similarities in expressed loci and/or tissue specificity with other vertebrates were found for several enzymes (ADH, FBALD, GAPDH, G3PDH, G6PDH, PGM and SOD). Differences were observed in the other enzymes: in ALP (due to the absence of an intestinal specific form typical of fish, amphibians, reptiles, or birds); in GPI and MDH (due to the tissue expression in Australian lungfish also present in other primitive fish species). Furthermore the LDH‐B4 was active only in the heart and kidney, while the LDH‐A4 form was dominant in all tissues. Moreover, a third LDH‐C* gene was expressed in the liver and kidney. Overall, comparison with other previously described vertebrates shows that the tissue expressions of several enzymes are relatively conservative, while others have changed markedly in this primitive dipnoan species.