CATALYTIC CLEAVAGE OF VASOPRESSIN BY HUMAN BENCE-JONES PROTEINS AT THE ARGINYLGLYCINAMIDE BOND

Bence Jones proteins were capable of hydrolyzing a peptide bond betwee n arginine-8 and the C-terminal glycinamide of vasopressin. This pepti dolytic activity obeyed typical Michaelis-Menten kinetics and exhibite d optimal activity at pH 8.2 and K-m of 0.6-1.9 mM. The catalytic effi ciency, 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 enzy mes. These results suggest that slow proteolysis, especially in the re nal tubules which are 'saturated' with Bence Jones proteins, may have a pathophysiological significance for various nephropathies often asso ciated with multiple myeloma with Bence Jones proteinuria.