3-Methyl-L-histidine is an L-histidine derivative substituted by a methyl group at postion 3 on the imidazole ring. 3-Methyl-L-histidine is an endogenous human metabolite and is also produced by Saccharomyces cerevisiae. 3-Methyl-L-histidine is formed by methylation of histidine as a posttranslational modification of actin and myosin. 3-Methyl-L-histidine is more abundant in in myosin from white skeletal muscle than from myosin of red skeletal and smooth muscle. 3-Methyl-L-histidine is a product of the degradation of myofibrillar proteins.