Activity of cathepsins during beef aging related to mutations in the myostatin gene

Double-muscled syndrome in cattle improves meat tenderness. However, the nature of the proteolytic processes associated with this phenomenon remains unknown. The aim of this study was to monitor changes in the activity of cathepsins (13, B + L, D and H) during meat aging and their gradual release from lysosomes to the cytosol in the longissimus muscle of yearling bulls of two breeds from northern Spain (Asturiana de los Valles and Asturiana de la Montana) showing three genotypes for muscular hypertrophy (mhlmh, mhl+ and +/+). The data showed that the pattern of cathepsin activity during meat aging paralleled variations in tenderness in the different genotypes studied. Maximal cathepsin D activity and minimal cathepsin H activity were recorded during meat aging times ranging from 3 to 21 days. The activities of cathepsins B and B + L were lower than that of cathepsin D at the established time points (3, 7, 14 and 21 days post-slaughter). The role of these enzymes in the activation of cathepsin D is discussed. All cathepsins showed similar action patterns, with high levels early on in the aging process and lower levels at later times. This pattern depended on the genotype and was significantly faster (P <= 0.05) in meat from mhlmh animals, intermediate in meat from mhl+ animals and slower in meat from normal (+/+) animals of both breeds. (c) 2006 Society of Chemical Industry