Serum calcium‐decreasing factor (caldecrin) from porcine pancreas has proteolytic activity which has no clear connection with the calcium decrease

Abstract

WC purified a grurtl calcium-decreasing factor, which showed chymotrypsin.;ikc proteasc activity, from porcine pancreas to homogeneity, The factor administered to mice intravenously at a dose of 20 pdkg b.w. decreased serum calcium by 15%. Treatment of the factor with the serine protease inhibitor, PMSF, caused a leftward shilt in the dose-response curve, showing strengthcncd activity. It also caused a decrease in serum calcium and hydroxyprolinc levels in rats, At a dose of IG ngml, the factor inhibited 15Ca release from cultured fetal long bone stimulated by parathyroid hormone (PTH) and PTH-related protein, but not by interleukin-lu. prostaglandin E, and 1,25sdihydroxy vilamin D,. No other well-known pancreatic proteases had these effects. In view of the results of experiments using protease inhibitor and pancreatic proteases, and in view of the specificity of this factor in vitro, we propose that Ihe l&tor exerts its serum calcium-decreasing activity most probably not through proleolytic degradation of PTH, but through an inhibition of PTH action on bones by a yet undefined mechanism.

Caldecrin: A pancreas-derived hypocalcemic factor, regulates osteoclast formation and function

“…The administration of purified porcine and rat caldecrin via the tail vein of mice decreased their serum calcium concentration dose-dependently and the maximum effect was attained 2-4 h post-injection with 20-100 µg (about 0.7-3.6 nmol)/kg body weight. The hypocalcemic potency of caldecrin was almost equivalent to that of porcine calcitonin (1 nmol/kg body weight, Tomomura et al [10] data not shown). The caldecrin proform (pro calderon), purified from the porcine pancreas in the presence of diisopropyl fluorophosphate, appeared to show time-and concentration-dependent chymotryptic activity following cleavage by trypsin.…”

“…The caldecrin-induced serum calcium decrease occurred concomitantly with a decrease in the serum concentration of hydroxyproline, which is a marker of bone resorption. This observation suggested that this serum calcium decrease may be due to the suppression of bone resorption [10] . The effects of caldecrin on osteoclast function have also been investigated; recombinant wildtype and protease activity-deficient mutant caldecrin produced concentration-dependent suppression of bone resorption in isolated rabbit mature osteoclasts [23] .…”

“…After tryptic activation, caldecrin changes its structure to a substrate-accessible catalytic cleft form. Active caldecrin hydrolyzes the leucyl bond (e.g., in the N-Succinyl-Ala-Ala-Pro-Leu-p-nitroanilide substrate) more efficiently than chymotrypsin A and B; Caldecrin also cleaves the phenylalanyl bond (e.g., in the N-Succinyl-Ala-Ala-Pro-Phe-p-nitroanilide substrate) and the tyrosyl bond (e.g., in the N-Succinyl-Leu-LeuVal-Tyr-p-nitroanilide substrate) [10,[19][20][21] . The protease activity of caldecrin is inhibited by serine protease inhibitors (phenylmethylsulfonyl fluoride or diisopropyl fluorophosphate), chymotrypsin inhibitor (chymostatin), and the Bowman-Birk trypsin and chymotrypsin inhibitor.…”

“…Caldecrin produces dose-dependent decreases in serum calcium concentrations [10] . The administration of purified porcine and rat caldecrin via the tail vein of mice decreased their serum calcium concentration dose-dependently and the maximum effect was attained 2-4 h post-injection with 20-100 µg (about 0.7-3.6 nmol)/kg body weight.…”

“…In the 1960's, the pioneering work of Takaoka et al [8,9] demonstrated that a porcine pancreatic extract had hypocalcemic activity. In 1992, we first successfully purified a hypocalcemic factor named caldecrin from a pancreatic extract using chromatographic separation techniques including ion exchange, gel filtration chromatography, and high-performance liquid chromatography [10] . To identify caldecrin, each fraction was intravenously administered to overnight-fasted mice and serum calcium concentrations were measured 4 h postinjection.…”