Preparative purification of dipeptidyl peptidase IV

Dipeptidyl-Peptidase IV was purified from pig kidney by ammonium sulfate fractionation, gel filtration, QAE-cellulose chromatography and affinity columns with Gly-Pro- and Concanavalin A-Sepharose. The specific activity of the purified enzyme is 41.8 units/mg. Polyacrylamide gel electrophoresis and silver staining show a single band. The enzyme preparation is free of aminopeptidase and dipeptidase activity, proved fluorimetrically and by gas chromatography/mass spectrometry. The most important procedure for removal of contaminating enzyme activities is a stepwise NaCl-gradient on a QAE-ZetaPrep ion exchange disk.

Rapid purification of dipeptidyl peptidase IV from rat liver plasma membrane

Dipeptidyl peptidase IV (EC 3.4.14.5) was solubilized from rat liver plasma membranes with sulphobetaine 14 and purified by successive affinity chromatography on Con A-Sepharose, wheat germ lectin-Sepharose and arginine-Sepharose columns. The specific activity of the final preparation was 49.4 mumol Gly-Pro p-nitroanilide/min per mg protein, representing a 1098-fold purification of the homogenate. SDS-polyacrylamide gel electrophoresis of the arginine-Sepharose eluate showed a single protein band with a molecular weight of 105,000. The isoelectric point was determined to be 3.9 under non-denaturing conditions with sulphobetaine 14. The preparation was free of post-proline cleaving enzyme. The content of aminopeptidase M was 0.2% of the total protein.

Purification and characterization of X-prolyl-dipeptidyl-aminopeptidase from Lactobacillus lactis and from Streptococcus thermophilus

X-Prolyl-dipeptidyl-aminopeptidase recently was found in several lactic acid bacteria. This article describes the purification of the enzymes from Lactobacillus lactis and Streptococcus thermophilus and compares their characteristics. Enzymes from both strains are serine-peptidases. They both have a molecular weight of about 165,000 daltons, an isoelectric point near 4.5, and are constituted of two subunits. The pH optimum of the enzyme isolated from L. lactis is 7.0, whereas the enzyme from S. thermophilus possesses a broad pH optimum between 6.5 and 8.2 with glycyl-L-prolyl-aminomethylcoumarin as substrate. Below pH 5, both enzymes are unstable; however, that from S. thermophilus is more rapidly denatured. The enzyme from S. thermophilus is more sensitive to heat than the corresponding enzyme from L. lactis. Enzymes from the both strains have different specificities towards various substrates and are differently effected by metals, chelators, and other inhibitors. The importance of this enzyme for the metabolism of lactic acid bacteria is discussed.

Dipeptidyl peptidases in bovine reproductive organs and secretions

Dipeptidyl peptidases (DPP) I-IV were analysed in homogenates of bovine reproductive organs as well as in seminal vesicle secretions and seminal plasma. The presence of various molecular forms of these enzymes was studied by fractionation using gel filtration, anion exchange chromatography and chromatofocusing. The eluting enzymes were pooled, and their biochemical properties were briefly characterized. The histochemical localization of DPP II and IV was carried out with the most active tissues. DPP I and III were absent from seminal plasma, but their highest activity was found in the epididymis and increased during sexual maturation. DPP II was found mainly in a single molecular form and displayed a wide distribution in the reproductive organs. Its activity in seminal plasma may be derived from various organs, although the major sources are probably the apical activity in the epididymis, ampulla and seminal vesicle. DPP IV activity was high in the cauda epididymis, and ampulla, and in the seminal vesicles and their secretions. The high activity of DPP IV in seminal plasma appeared to derive from these organs, which showed a strong apical reaction of the epithelial lining. In seminal vesicles the enzyme was mainly secreted attached to membrane particles called vesiculosomes.

A simple method for the purification of dipeptidyl aminopeptidase IV from porcine kidney using HPLC

Dipeptidyl aminopeptidase IV (E.C. 3.4.14.5) has been purified to homogeneity using "soft-column" chromatography on Sephadex G-200, DEAE-cellulose, gly-pro-AH-Sepharose and finally HPLC on TSK G-3000SW. The purification by HPLC is fast and gives a better yield of pure enzyme than procedures which have been described previously. The enzyme obtained in this manner has a high specific activity (86 U/mg using a saturating level of gly-pro-4-nitroanilide as substrate) and was free of contaminating peptidase activities. Our preparation of DAP IV is suitable for peptide sequencing studies by fast atom bombardment mass spectrometry.

Involvement of plasma membrane dipeptidyl peptidase IV in fibronectin-mediated adhesion of cells on collagen

Dipeptidyl peptidase IV is an exopeptidase found in the serum and in plasma membranes of most animal tissues. The role of this enzyme in cell-matrix interaction of BHK cells and hepatocytes grown on collagen-coated surfaces was investigated by three different approaches. 1) Glass surfaces were derivatized with bovine serum albumin which resulted in a cell-repulsing substratum. When it was further modified with Gly-Pro-Ala tripeptide, which is a substrate for dipeptidyl peptidase IV, BHK fibroblasts spread on it rapidly. The spreading could be inhibited by addition of free Gly-Pro-Ala or other substrates of the enzyme as well as by an inhibitor peptide Val-Pro-Leu. It was not influenced by tripeptides which were neither substrates nor inhibitors of dipeptidyl peptidase IV. 2) The addition of Gly-Pro-Ala to seeded cells slowed down the initial process of cell spreading on denatured collagen in the presence of fibronectin. The presence of both collagen and fibronectin was a necessary precondition for the spreading of cells in a manner sensitive to Gly-Pro-Ala. 3) Antiserum raised against mouse liver dipeptidyl peptidase IV added to the medium delayed the spreading of rat hepatocytes on denatured collagen in the presence of fibronectin in a manner similar to when Gly-Pro-Ala was added to the medium. These observations lead to the conclusion that plasma membrane dipeptidyl peptidase IV may be involved in the initial phase of fibronectin-mediated cell spreading on collagen.