“…Members of this enzyme family play a key role in animals as ATP buffering systems in cells that display high and variable rates of ATP turnover [Kenyon and Reed, 1983;Wyss et al, 1992;Ellington, 2001]. AK is most widely distributed among organisms; its activity has been observed in arthropods, molluscs, nematoda, cnidarians, poriferae (the most ancient multi-cellular organisms), protozoans (ciliates, Trypanosoma and choanoflagellates) and bacteria [Watts and Bannister, 1970;Noguchi et al, 2001;Pereira et al, 2000;Uda et al, 2006;Conejo et al, 2008;Andrews et al, 2008], indicating an ancient origin of AK. Most AKs are monomers with a relative molecular mass of approximately 40 kDa [Morrison, 1973].…”