Gene structure of the two-domain taurocyamine kinase from Paragonimus westermani: Evidence for a distinct lineage of trematode phosphagen kinases

• Phylogenetic analyses showed that trematode TKs form a distinct clade from protist and annelid TKs.
• Comparison of intron boundaries provided more evidence that trematode TKs evolved from an AK gene.
• Trematode TKs possibly interact with a larger yet to be identified phosphagen kinase.
• Data presented provide insights on the evolution of phosphagen kinases, especially those found in trematodes.

Taurocyamine kinase (TK) is an enzyme that catalyzes the reversible transfer of a phosphate between ATP and taurocyamine. Annelid TKs were suggested to have evolved from a CK ancestor. However, TKs from the lung fluke Paragonimus westermani comprised another lineage. Construction of phylogenetic tree and comparison of exon/intron organization showed that P. westermani TK and other trematode TKs evolved from a molluscan arginine kinase (AK) gene. Exon shuffling probably caused the changes in amino acid sequence thereby changing the affinity from AK to TK. The present study provides new insights on the evolution of phosphagen kinases found in trematodes.