Tenderness--an enzymatic view.

One of the most common causes of unacceptability in meat quality is toughness. Toughness is attributed to a range of factors including the amount of intramuscular connective tissue, intramuscular fat, and the length of the sarcomere. However, it is apparent that the extent of proteolysis of key proteins within muscle fibres is significant determinant of ultimate tenderness.

Expression of calpastatin isoforms in muscle and functionality of multiple calpastatin promoters.

Calpastatin is the specific endogenous inhibitor of calpain proteinase that is encoded by a single gene. Transient transfection assays in both a non-fusing skeletal muscle and non-muscle cell-line demonstrated that the putative porcine calpastatin promoter regions 5' to exons 1xa, 1xb, and 1u were functional. Both real-time quantitative and semi-quantitative RT-PCR on porcine skeletal muscle total RNA indicated that steady-state expression of Type I and III mRNAs containing exons 1xa and 1u, respectively, was at equivalent levels whilst the expression of Type II mRNA containing exon 1xb was significantly less (p<0.