Protein: Synthesis and Turnover

Whole-body protein homeostasis is regulated acutely at the level of tissue protein synthesis and proteolysis in relation to feeding and fasting and chronically through the linkage between long bone growth and muscle growth, both subject to adequate protein intakes. Protein turnover, mediated by several proteolytic systems, is studied with various isotope tracer models which have revealed much about its extent and its physiological implications. Regulation of protein turnover operates at the levels of gene expression, ribosomal concentrations and activity especially initiation of translation, and proteolysis and is mediated mainly by amino acids and insulin which together ensure efficient postprandial protein utilization.