Conservation of group XII phospholipase A2 from bacteria to human

Vertebrate group XII phospholipases A2 (GXII PLA2, conserved domain pfam06951) are proteins with unique structural and functional features within the secreted PLA2 family. In humans, two genes (GXIIA PLA2 and GXIIB PLA2) have been characterised. GXIIA PLA2 is enzymatically active whereas GXIIB PLA2 is devoid of catalytic activity. Recently, putative homologues of the vertebrate GXII PLA2s were described in non-vertebrates. In the current study a total of 170 GXII PLA2 sequences were identified in vertebrates, invertebrates, non-metazoan eukaryotes, fungi and bacteria. GXIIB PLA2 was found only in vertebrates and the searches failed to identify putative GXII PLA2 homologues in Archaea. Comparisons of the predicted functional domains of GXII PLA2s revealed considerable structural identity within the Ca2 +-binding and the catalytic sites among the various organisms suggesting that functional conservation may have been retained across evolution. The preservation of GXII PLA2 family members from bacteria to human indicates that they have emerged early in evolution and evolved via gene/genome duplication events prior to Eubacteria. Gene duplicates were identified in some invertebrate taxa suggesting that species-specific duplications occurred. The analysis of the GXII PLA2 homologue genome environment revealed that gene synteny and gene order are preserved in vertebrates. Conservation of GXII PLA2s indicates that important functional roles involved in species survival and were maintained across evolution and may be dependent on or independent of the enzyme's phospholipolytic activity.