Evolutionary history of the enolase gene family

The enzyme enolase [EC 4.2.1.11] is found in all organisms, with vertebrate s exhibiting tissue-specific isozymes encoded by three genes: alpha (alpha) , beta (beta), and gamma (gamma) enolase. Limited taxonomic sampling of eno lase has obscured the timing of gene duplication events. To help clarify th e evolutionary history of the gene family, cDNAs were sequenced from six ta xa representing major lineages of vertebrates: Chiloscyllium punctatum (sha rk), Amia calva (bowfin), Salmo trutta (trout), Latimeria chalumnae (coelac anth), Lepidosiren paradoxa (South American lungfish), and Neoceratodus for steri (Australian lungfish). Phylogenetic analysis of all enolase and relat ed gene sequences revealed an early gene duplication event prior to the las t common ancestor of living organisms. Several distantly related archaebact erial sequences were designated as 'enolase-2', whereas all other enolase s equences were designated 'enolase-1'. Two of the three isozymes of enolase- 1, alpha- and beta -enolase, were discovered in actinopterygian, sarcoptery gian, and chondrichthian fishes. Phylogenetic analysis of vertebrate enolas es revealed that the two gene duplications leading to the three isozymes of enolase-1 occurred subsequent to the divergence of living agnathans, near the Proterozoic/Phanerozoic boundary (approximately 550 Mya). Two copies of enolase, designated cc, and a,, were found in the trout and are presumed t o be the result of a genome duplication event. (C) 2000 Elsevier Science B. V. All rights reserved.