Enzyme responsible for the N-acetyl-histidine (NAH) synthesis, which is a major constituent of brain and lens of ectothermic vertebrates. acetyl-CoA + L-histidine = CoA + H(+) + N(alpha)-acetyl-L-histidine Strong histidine N-acetyltransferase activity has been detected in ectothermic vertebrates and not in endothermic birds and mammals.