Isolation of pancreatic trypsin inhibitor from bovine pituitary glands

Identification and immunohistochemical localization of various bovine pancreatic trypsin inhibitor-isoforms in bovine pituitary gland

Three isoinhibitors of bovine pancreatic trypsin inhibitor (BPTI) have been identified and isolated from bovine pituitary gland. The results of the purification process by affinity chromatography on immobilized trypsin, the electrophoretic mobility in non-denaturing conditions, the antiproteolytic activity and the immunochemical reactions indicate that these inhibitors correspond to those previously isolated from bovine spleen and lung. In addition, immunohistochemical experiments show that the isoinhibitors and BPTI are exclusively localized in the mast cells, and not in the endocrine cells, of the pars intermedia and posterior lobe (neurohypophysis) of the pituitary gland. The physiological implications of these findings are discussed.

Cystatins from bovine brain: purification, some properties, and action on substance P degrading activity

Two cystatins were purified from tissue extract of bovine brain by alkaline treatment, acetone fractionation, gel chromatography on Sephadex G-75, and affinity chromatography on S-carboxymethyl-papain-Sepharose. One of the inhibitors had a relatively high molecular mass, 25 kDa (HMM-cystatin) with pI 4.7, and the other, 11 kDa (LMM-cystatin) with pI 5.23. Both inhibitors showed considerable stability at pH 2 and 80 degrees C. The cystatins inhibited papain, ficin, and cathepsins B and H, but not trypsin, chymotrypsin, thermolysin, nagarse, and cathepsin D. Ki values for the complexes of papain and the inhibitors were estimated to be 2.8 x 10(-10) M for HMM-cystatin and 1.3 x 10(-9) M for LMM-cystatin. Both purified cystatins prevented degradation of substance P by soluble fraction and lysosomal extract obtained from synaptosomes, but did not suppress the cleavage of the peptide by synaptosomal plasma membranes.

Schwann cell proliferation and localized proteolysis: expression of plasminogen-activator activity predominates in the proliferating cell populations

The role of the serum proteolytic system plasminogen/plasminogen activator as a biochemical tool used by the glia or neurons, or both, for maintaining their temporary and flexible cellular interactions during histogenesis of the nervous system is under study. The present report identifies a glia cell type, the Schwann cell, as one of the cellular components of the nervous system that uses extracellular proteolysis at the time of the tissue construction. Purified dividing mouse Schwann cells in culture produce extracellular plasminogen activator. The levels of extracellular plasminogen-activator activity, as measured by the biochemical fibrinolytic assay, were directly related to the proliferation rates of the Schwann cells. The cellular plasminogen-activator specific activity at the maximal rate of cell proliferation was 3-4 times higher than that of the cells at low rate of mitosis. It is concluded that plasminogen-activator activity is expressed predominantly by the proliferating Schwann cell populations, suggesting that the extracellular proteolysis is used by the tissue at those stages when the cells divide.