CARNMT1 (carnosine N-methyltransferase 1) is a dual-function methyltransferase with roles in both peptide and protein methylation. Its primary characterized function catalyzes anserine formation from carnosine through S-adenosylmethionine-dependent N-methylation 1. CARNMT1 methylates histidine residues in carnosine, homocarnosine, and other L-histidine-containing dipeptides and tripeptides, with activity distributed across cytosolic and nuclear compartments 1. Beyond peptide metabolism, CARNMT1 functions as a protein histidine methyltransferase (HMT) with context-dependent substrate specificity 2. It preferentially methylates C3H zinc finger proteins including U2AF1, ZC3H15, ZC3H18, RBM22, PPP1R10, PRR3, and RNF113A, stabilizing their zinc finger structures and regulating RNA binding functions 23. In human tissues, anserine is present at low micromolar concentrations, with skeletal muscle containing approximately 15-fold higher levels than cardiac muscle, though CARNMT1 expression in skeletal muscle is notably poor 4. Pathologically, CARNMT1 variants have been identified in autosomal recessive neurodevelopmental disorder families with intellectual disability, localized within previously reported ID microdeletion regions 5. Additionally, CARNMT1 is subject to HDAC1-mediated deacetylation, indicating post-translational regulation 6.