Partial characterization of a highly conserved aspartyl kinase (AK) in normal human liver

Subcellular fractions from human liver were assayed for aspartyl kinase (AK) activity measured by standard spectrophotometric methods. Along the purification procedure three different fractions displayed the expected enzyme activity. Interestingly, two of these fractions were specifically recognized by antibodies raised against E. coli aspartate kinases, suggesting a high degree of evolutionary conservation for these ubiquitous enzymes for prokaryotes. Since their known function in bacteria is not strictly required in eukaryotes, these observation imply that the presence and activity of aspartyl kinase(s) in mammals might represent putative regulatory roles for these enzymes in eukaryotic cell metabolism.