Effect of Lysosomal Cathepsin L on Proteolysis of Beef Myofibrillar Proteins In Vivo and In Vitro.

Baowei Cui,Xiangren Meng,Xiuyun Guo,Yawei Zhang

doi:10.3390/foods11040613

Abstract

This study investigated the effects of cathepsin L on proteolysis of beef myofibrillar proteins in vivo and in vitro. Results indicated that cathepsin L affected the degradation of desmin and troponin-T during postmortem aging, and the extent of degradation increased from 1 d to 14 d postmortem. No detectable degradation of titin, nebulin, and α-actinin in the presence of cathepsin L inhibitor was observed during postmortem aging. In vitro, cathepsin L affected the degradation of titin, nebulin, and troponin-T, and the extent of degradation increased with increasing incubation time. Nevertheless, cathepsin L did not cause the degradation of α-actinin and desmin, regardless of incubation temperature. The different results between in vitro and in vivo experiments might mainly depend on different treatment temperatures. Overall, these results indicated that cathepsin L participated in the degradation of myofibrillar proteins and meat tenderization.

Highlights

Tenderness is generally considered to be the most important sensorial attribute for consumers regarding meat consumption [1,2]
This study demonstrated that cathepsin L (CAT) participated in the degradation of myofibrillar proteins (MPs) both in vivo and in vitro
CAT caused the degradation of titin and nebulin in vitro, the extent of which increased with increased incubation temperature, but had no effect on the degradation of these MPs in vivo

Summary

Introduction

Tenderness is generally considered to be the most important sensorial attribute for consumers regarding meat consumption [1,2]. Meat tenderness is mainly determined by the proteolysis of key myofibrillar and cytoskeletal proteins, such as titin, nebulin, α-actinin, desmin, troponin-T, dystrophin, and vinculin during the postmortem aging [4,5,6]. Endogenous proteolytic enzymes (e.g., calpains, caspases, and lysosomal proteinases) are of crucial importance for the postmortem proteolysis of the key myofibrillar and cytoskeletal proteins, and in meat tenderization [7,8]. Cathepsins, which are located in the lysosomes of muscle cells, and potentially released during postmortem aging, are favored by postmortem cells, and play an important role in proteolysis and meat tenderization [9]. Previous studies have shown that cathepsin L (CAT) can degrade myofibrillar proteins (MPs) in vitro [8,10]. Several studies have shown that CAT has no effect on MPs proteolysis and meat tenderness in vivo. Koohmaraie et al [13] conclude, from sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) patterns, that

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