Probable N-acetyltransferase. Shows only trace activity toward L-His and no N-acetyltransferase activity toward other amino acids. The physiological substrate of this enzyme is unknown. NAT16 is the ortholog of the ectothermic vertebrates enzyme HISAT (AC I3J7Q8) responsible for the synthesis of N-acetyl-histidine (NAH). NAT16 protein, unlike fish HISAT, has only trace enzyme activity for NAH synthesis.