“…The only other report in the literature we are aware of is by Gewitz et al (37), who reacted free L-histidine with L-amino acid oxidase and horseradish peroxidase to yield 4(5)-imidazolecarboxaldehyde, 4(5)-imidazolecarboxylic acid, carbon dioxide, ammonia, and hydrogen peroxide. 4(5)-imidazolecarboxaldehyde is commercially available and can be prepared through a variety of synthetic pathways (37)(38)(39)(40)(41)(42)(43)(44)(45)(46)(47)(48)(49), which are different from the oxidation of L-histidine currently being discussed. Fig.…”