Anserine and related dipeptides

Carnosine belongs to a family of histidine-containing dipeptides. The family members differ in small ways that change how they behave.

• Anserine (beta-alanyl-N-methylhistidine) is carnosine with a methyl group on the imidazole ring. The enzyme CARNMT1 adds it. Anserine is the main dipeptide in chicken, turkey, tuna and bonito, and it occurs in human kidney. It is broken down more slowly by serum carnosinase than carnosine, which is why trace anserine appears in blood after a chicken meal while carnosine does not (Wikipedia: Anserine; Jones, Smith and Harris 2011). Trials of an anserine-carnosine mixture in older adults are listed at Hisatsune 2016, Rokicki 2015 and Szcześniak 2014.
• Balenine, also called ophidine, is the other methylated form. It was named ophidine when found in snake muscle and balenine when found in whale muscle (Progress in Neurobiology 1999). Anserine and balenine differ in which ring nitrogen carries the methyl group, and the literature is not consistent about how it numbers them, so this site defines each by structure rather than by number.
• Homocarnosine replaces beta-alanine with GABA. It is the dominant form in the human brain, where carnosine itself is low or absent except in the olfactory bulb.
• Carcinine (beta-alanyl-histamine) is carnosine with its carboxyl group removed.
• N-acetylcarnosine has its own page: N-acetylcarnosine.

Humans are unusual in holding carnosine without a methylated variant in muscle. Most other animals carry anserine or balenine alongside it (Boldyrev, Aldini and Derave 2013). Dogs and cats hold mostly anserine.