Catalytic cleavage of vasopressin by human Bence Jones proteins at the arginylglycinamide bond

Bence Jones proteins were capable of hydrolyzing a peptide bond between arginine-8 and the C-terminal glycinamide of vasopressin. This peptidolytic activity obeyed typical Michaelis-Menten kinetics and exhibited optimal activity at pH 8.2 and K-m of 0.6-1.9 mM. The catalytic efficiency, k(cat)/K-m, was calculated to be 0.8 to 5.8 min(-1) M(-1). The Bence Jones proteins displayed turnover, an essential feature of enzymes. These results suggest that slow proteolysis, especially in the renal tubules which are 'saturated' with Bence Jones proteins, may have a pathophysiological significance for various nephropathies often associated with multiple myeloma with Bence Jones proteinuria.