In the 1964–1970 window, protein degradation began to be viewed as a central regulator of cell physiology, operating across bacteria, liver, muscle, and nucleus. Methodological advances enabled direct measurement of degradation rates, notably perfusion-based assays to quantify turnover in living cells and pulse-labeling approaches that track radiolabeled proteins. This convergence of techniques and observations established protein degradation as a unifying mechanism shaping proteome composition, organelle maintenance, and tissue remodeling, linking nutritional and developmental states to turnover dynamics.