Calpains and Tenderness
Calpains are the enzymes that weaken muscle fibers during the break down of proteins. Calpastatin is the enzyme that regulates the activity of Calpain; the balance between Calpain and Calpastatin regulates the rate of muscle growth.
Genes in DNA sequencing attributed to tenderness are calpain (CAPN1) and calpastatin (CAST). Muscle mass in cattle is in a continual cycle of synthesis and breakdown. Increasing muscle mass occurs when the rate of synthesis is greater than the rate of breakdown of proteins in the muscle tissue.
After harvest, the calpains continue the breakdown of protein in muscle fibers resulting in the natural process of ‘tenderizing’. Higher levels of calpastatin result in the reduction of the amount of calpains and inhibit the breakdown of proteins, thus the meat will be less tender. The relationship between calpains and calpasatin after harvest is the natural process of improving beef through aging.
Tenderness is passed down through heredity and selective breeding. The incorporation of tenderness traits in DNA validation testing is designated by a number on a scale of 1 to 10 – with the most tender. 59% of the population of Wagyu cattle have scores of 1 to 5 and 41% have scores of 6 to 10.
Tenderness Scores in Population of Wagyu