Human liver iduronate-2-sulphatase. Purification, characterization and catalytic properties.

Human iduronate-2-sulphatase (EC 3.1.6.13), which is involved in the lysosomal degradation of the glycosaminoglycans heparan sulphate and dermatan sulphate, was purified more than 500,000-fold in 5% yield from liver with a six-step column procedure, which consisted of a concanavalin A-Sepharose-Blue A-agarose coupled step, chromatofocusing, gel filtration on TSK HW 50S-Fractogel, hydrophobic separation on phenyl-Sepharose CL-4B and size separation on TSK G3000SW Ultrapac. Two major forms were identified. Form A and form B, with pI values of 4.5 and less than 4.0 respectively, separated at the chromatofocusing step in approximately equal amounts of recovered enzyme activity. By gel-filtration methods form A had a native molecular mass in the range 42-65 kDa. When analysed by SDS/PAGE, dithioerythritol-reduced and non-reduced form A and form B consistently contained polypeptides of molecular masses 42 kDa and 14 kDa. Iduronate-2-sulphatase was purified from human kidney, placenta and lung, and form A was shown to have similar native molecular mass and subunit components to those observed for liver enzyme. Both forms of liver iduronate-2-sulphatase were active towards a variety of substrates derived from heparin and dermatan sulphate. Kinetic parameters (Km and Kcat) of form A were determined with a variety of substrates matching structural aspects of the physiological substrates in vivo, namely heparan sulphate, heparin and dermatan sulphate. Substrate with 6-sulphate esters on the aglycone residue adjacent to the iduronic acid 2-sulphate residue being attack were hydrolysed with catalytic efficiencies up to 200 times above that observed for the simplest disaccharide substrate without a 6-sulphated aglycone residue. The effect of incubation pH on enzyme activity towards the variety of substrates evaluated was complex and dependent on substrate aglycone structure, substrate concentration, buffer type and the presence of other proteins. Sulphate and phosphate ions and a number of substrate and product analogues were potent inhibitor of form A and form B enzyme activities.     

Human liver alpha-L-fucosidase. Purification, characterization, and immunochemical studies.

Human liver alpha-L-fucosidase has been purified 6300-fold to apparent homogeneity with 66% yield by a two-step affinity chromatographic procedure utilizing agarose epsilon-aminocaproyl-fucosamine. Isoelectric focusing revealed that all six isoelectric forms of the enzyme were purified. Polyacrylamide gel electrophoresis of the purified alpha-L-fucosidase demonstrated the presence of six bands of protein which all contained fucosidase activity. The purified enzyme preparation was found to contain only trace amounts of seven glycosidases. Quantitative amino acid analysis was performed on the purified fucosidase. Preliminary carbohydrate analysis indicated that only about 1% of the molecule is carbohydrate. Gel filtration on Sepharose 4B indicated an approximate molecular weight for alpha-L-fucosidase of 175,000 +/- 18,000. High speed sedimentation equilibrium yielded a molecular weight of 230,000 +/- 10,000. Sodium dodecyl sulfate polyacrylamide gels indicated the presence of a single subunit of molecular weight, 50,100 +/- 2,500. The enzyme had a pH optimum of 4.6 with a suggested second optimum of 6.5. Apparent Michaelis constants and maximal velocities were determined on the purified enzyme with respect to the 4-methylumbelliferyl and the p-nitrophenyl substrates and were found to be 0.22 mM and 14.1 mumol/mg of protein/min and 0.43 mM and 19.6 mumol/mg of protein/min, respectively. Several salts had little or no effect on fucosidase activity although Ag+ and Hg2+ completely inactivated the enzyme. Antibodies made against the purified fucosidase were dound to be monospecific against crude human liver supernatant fluids and the pure antigen. No cross-reacting material was detected in the crude liver supernatant fluid from a patient who died with fucosidosis.     

Purification and some properties of the D-lactate-2-sulphatase of Pseudomonas syringae GG.

A soil bacterium grown on propan-2-yl sulphate as sole source of carbon and sulphur yielded extracts containing an enzyme capable of liberating sulphate from racemic lactate-2-sulphate. The enzyme was purified to homogeneity by a combination of streptomycin sulphate precipitation of nucleic acids, batch treatment with DEAE-cellulose, and chromatography on columns of DEAE-cellulose, Sephacryl S-300 and butyl-agarose. The protein was monomeric with an Mr of 55 000-60 000. The enzyme activity was specific for D-lactate-2-sulphate (Km 6.6 nM; maximal specific activity 14.3 mumol/min per mg of protein) and showed no activity towards the L-isomer. The products of the enzyme's action were inorganic sulphate and D-lactate which were released in equimolar amounts and stoicheiometrically with the amount of ester hydrolysed. No L-lactate was formed. Retention of configuration implied cleavage of the O-S bond of the C-O-S ester link and this was confirmed by 18O-incorporation experiments in which 18O from 18O-enriched water in the incubation medium was incorporated exclusively and quantitatively into inorganic sulphate. Only two other esters (serine-O-sulphate and p-nitrophenyl sulphate) of a total of 29 compounds tested were substrates for the enzyme. D-Lactate, L-lactate-2-sulphate and the substrate analogues glycollate-2-sulphate and butyrate-2-sulphate were significantly inhibitory.     

Purification of porcine liver pyruvate dehydrogenase complex and characterization of its catalytic and regulatory properties.

Procedures are described for isolating highly purified porcine liver pyruvate and α-ketoglutarate dehydrogenase complexes. Rabbit serum stabilized these enzyme complexes in mitochondrial extracts, apparently by inhibiting lysosomal proteases. The complexes were purified by a three-step procedure involving fractionation with polyethylene glycol, pelleting through 12.5% sucrose, and a second fractionation under altered conditions with polyethylene glycol. Sedimentation equilibrium studies gave a molecular weight of 7.2 × 10⁶ for the liver pyruvate dehydrogenase complex. Kinetic parameters are presented for the reaction catalyzed by the pyruvate dehydrogenase complex and for the regulatory reactions catalyzed by the pyruvate dehydrogenase kinase and pyruvate dehydrogenase phosphatase. For the overall catalytic reaction, the competitive K_i to K_m ratio for NADH versus NAD⁺ and acetyl CoA versus CoA were 4.7 and 5.2, respectively. Near maximal stimulations of pyruvate dehydrogenase kinase by NADH and acetyl CoA were observed at NADH:NAD⁺ and acetyl CoA:CoA ratios of 0.15 and 0.5, respectively. The much lower ratios required for enhanced inactivation of the complex by pyruvate dehydrogenase kinase than for product inhibition indicate that the level of activity of the regulatory enzyme is not directly determined by the relative affinity of substrates and products of catalytic sites in the pyruvate dehydrogenase complex. In the pyruvate dehydrogenase kinase reaction, K⁺ and NH⁺₄ decreased the K_m for ATP and the competitive inhibition constants for ADP and (β,γ-methylene)adenosine triphosphate. Thiamine pyrophosphate strongly inhibited kinase activity. A high concentration of ADP did not alter the degree of inhibition by thiamine pyrophosphate nor did it increase the concentration of thiamine pyrophosphate required for half-maximal inhibition.     

Human liver N-acetylglucosamine-6-sulphate sulphatase. Purification and characterization.

Human N-acetylglucosamine-6-sulphate sulphatase was purified at least 50,000-fold to homogeneity in 78% yield from liver with a simple three-step four-column procedure, which consists of a concanavalin A-Sepharose/Blue A-agarose coupled step, chromatofocusing and Cu2+-chelating Sepharose chromatography. In all, four forms were isolated and partially characterized. Forms A and B, both with a pI greater than 9.5 and representing 30% and 60% respectively of the recovered enzyme activity, were separated by hydroxyapatite chromatography of the enzyme preparation obtained from the Cu2+-chelating Sepharose step. Both forms A and B had native molecular masses of 75 kDa. When analysed by SDS/polyacrylamide-gel electrophoresis, form A consists of a single polypeptide of molecular mass 78 kDa, whereas form B contained 48 kDa and 32 kDa polypeptide subunits. Neither form A nor form B was taken up from the culture medium into cultured human skin fibroblasts. The two other forms (C and D), with pI values of 5.8 and 5.4 respectively, represented approx. 7% and 3% of the total recovered enzyme activity. The native molecular masses of forms C and D were 94 kDa and approx. 75 kDa respectively. Form C contained three polypeptides with molecular masses of 48, 45 and 32 kDa. N-Acetylglucosamine-6-sulphate sulphatase activity was measured with a radiolabelled disaccharide substrate derived from heparin. The development of this substrate enabled the isolation and characterization of N-acetylglucosamine-6-sulphate sulphatase to proceed efficiently. Forms A, B and C had pH optima of 5.0, Km values of 11.7, 14.2 and 11.1 microM respectively and Vmax. values of 105, 60 and 53 nmol/min per mg of protein respectively. The molecular basis of the multiple forms of this sulphatase is not known. It is postulated that the differences in structure and properties of the four enzyme forms are due to differences in the state of processing of a large subunit.     

Guinea-pig liver leukotriene A4 hydrolase. Purification, characterization and structural properties

Leukotriene A4 hydrolase from perfused guinea-pig liver was purified 1200-fold to near homogeneity with a yield of about 20%. Apparent values of Km and Vmax at 37 degrees C (27 microM and 68 mumol x mg-1 x min-1), turnover number, and activation energy for the conversion of leukotriene A4 into leukotriene B4 were estimated from kinetic data obtained at -10 degrees C, 0 degree C and +10 degrees C (Arrhenius plots). Physical properties including Mr (67,000-71,000), pH optimum, isoelectric point and Stokes' radius were determined. The amino acid composition and N-terminal amino acid sequence were established after carboxymethylation of the enzyme. Unlike liver cytosolic epoxide hydrolase, the purified enzyme did not catalyze the conversion of leukotriene A4 into (5S,6R)-5,6-dihydroxy-7,9-trans-11,14-cis-icosatetraenoic acid.     

3-Hydroxy-3-methylglutaryl-coenzyme A synthase from ox liver. Purification, molecular and catalytic properties.

Mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase (EC 4.1.3.5) was purified to homogeneity from ox liver and obtained essentially free from acetoacetyl-CoA thiolase activity. The purification procedure included substrate elution from cellulose phosphate and chromatofocusing. The relative molecular mas was about 100 000 and S20,w0 was 6.36S. The enzyme appears to be a dimer of identical subunits (Mr 47 900). The Km for acetoacetyl-CoA is extremely low (less than 0.5 microM), and acetoacetyl-CoA (Acac-CoA) gives marked substrate inhibition (KiAcac-CoA = 3.5 microM) that is competitive with respect to acetyl-CoA. Both CoA and DL-3-hydroxy-3-methylglutaryl-CoA give mixed product inhibition with respect to acetyl-CoA, which is compatible with a Ping Pong mechanism in which both products can form kinetically significant complexes with two forms of the enzyme. The two forms are most likely to be free enzyme and an acetyl-enzyme intermediate.     

Human heparanase. Purification, characterization, cloning, and expression.

Heparan sulfate and heparan sulfate proteoglycans are present in the extracellular matrix as well as on the external cell surface. They bind various molecules such as growth factors and cytokines and modulate the biological functions of binding proteins. Heparan sulfate proteoglycans are also important structural components of the basement membrane. Heparanase is an endo-beta-D-glucuronidase capable of cleaving heparan sulfate and has been implicated in inflammation and tumor angiogenesis and metastasis. In this study, we report the purification of a human heparanase from an SV40-transformed embryonic fibroblast cell line WI38/VA13 by four sequential column chromatographies. The activity was measured by high speed gel permeation chromatography of the degradation products of fluorescein isothiocyanate-labeled heparan sulfate. The enzyme was purified to homogeneity, yielding a peptide with an apparent molecular mass of 50 kDa when analyzed by SDS-polyacrylamide gel electrophoresis. Using the amino acid sequences of the N-terminal and internal heparanase peptides, a cDNA coding for human heparanase was cloned. NIH3T3 and COS-7 cells stably transfected with pBK-CMV expression vectors containing the heparanase cDNA showed high heparanase activities. The homology search revealed that no homologous protein had been reported.     

Human alpha-fucosidase. Purification and properties.

Human placental alpha-fucosidase (EC 3.2.1.51) has been extensively purified and partially characterized with respect to kinetic and structured properties. Although the enzyme seems to be separated by DEAE-cellulose chromatography in two forms which differ in their molecular weight and thermostability, an interconversion between the two forms takes place during storage and/or electrofocusing so that the same peaks of activity, revealed by the latter technique, are found before and after DEAE-cellulose chrome. The heterogeneous peaks of activity revealed by isoelectrofocusing show a reproducible pattern in the different tissues examined, except in serum where their pI values are consistently more acidic.     

Human lung tryptase. Purification and characterization

Human lung tryptase, a mast cell-derived trypsin-like serine protease, has been isolated from whole human lung tissue obtained at autopsy. Increased yields from this purification process have allowed extensive characterization of the enzyme. One of the critical steps in the purification scheme is the use of a linear heparin gradient to elute active material from cellulose phosphate. Gel filtration studies in 1.0 M NaCl yielded an apparent Mr = 135,000, and subsequent electrophoresis on sodium dodecyl sulfate-polyacrylamide gels demonstrated the presence of two active species with apparent Mr = 30,900 and 31,600. Enzymatic activity was sensitive to NaCl concentrations above 0.05 M and was only 50% in 0.15 M NaCl, decreasing to 18% in 0.6 M NaCl. The effects of synthetic and natural inhibitors have also been studied, confirming the enzyme's trypsin-like characteristics and demonstrating that naturally occurring serum inhibitors are incapable of diminishing its activity. A complete amino acid analysis showed a high tryptophan content. Lastly, antisera to human lung tryptase have been generated, and the immunological identity of active fractions has been investigated as well as the localization of the enzyme to the mast cell granule by immunohistochemical staining.     

Purification and characterization of 2-oxoaldehyde dehydrogenase from rat liver.

The partial purification (123-fold) of 2-oxoaldehyde dehydrogenase (2-oxoaldehyde:NAD(P)+ oxidoreductase, 1.2.1.23) from rat liver was carried out using a purification procedure which involved (NH4)2SO4 fractionation, DEAE-Sephadex chromatography, Blue-Dextran affinity chromatography and CM-Sephadex chromatography. A single form of the enzyme was observed, mol. wt. approx. 50000 by gel chromatography. 2-Oxoaldehyde dehydrogenase appears to be highly specific for NADP+ and methylglyoxal. No activity is observed in the absence of certain amines which have vicinal amino and hydroxyl groups. The only known amine which activates the enzyme at physiological pH is L-serine methyl ester, suggesting that the regulation of this enzyme in vivo may require a derivative of serine.     

Purification and characterization of beta-N-acetylhexosaminidase I2 from human liver.

beta-N-Acetylhexosaminidase I2 was purified from human liver by a combination of concanavalin A chromatography, DEAE-cellulose chromatography, gel filtration and affinity chromatography on 2-acetamido-N-(6-aminohexanoyl)-2-deoxy-beta-D-glucopyranosylamine coupled to CNBr-activated Sepharose 4B. Its specific activity was 130 mumol/min per mg of protein compared with values of 150 and 320 mumol/min/mg of protein for beta-N-acetylhexosaminidases A and B purified from the same tissue. Km values for I2, A and B were 1.0 mM, 0.8 mM and 0.74 mM respectively. On gradient gel electrophoresis under non-denaturing conditions, hexosaminidase I2 behaved similarly to A and appeared to have an Mr between 100 000 and 110 000. beta-N-Acetylhexosaminidase I2 was resolved into two major polypeptides, of Mr 56 000 and 29 000, on SDS/polyacrylamide-gel electrophoresis under denaturing conditions. Immunoblotting with anti-(hexosaminidase alpha-subunit) serum confirmed that the 56 000-Mr component was the alpha-subunit and anti-(hexosaminidase B) serum reacted with the 29 000 Mr component. beta-N-Acetylhexosaminidase I2 more closely resembles form A than B, but the features of its structure that allow it to be separated from A on the basis of net charge have not yet been found.     

Purification and characterization of 2-enoyl-CoA reductase from bovine liver.

Mitochondrial 2-enoyl-CoA reductase from bovine liver was purified and characterized. A simple three-step purification was developed, involving ion-exchange chromatography to separate the bulk of the NADPH-dependent 2,4-dienoyl-CoA reductase, followed by chromatography on Blue Sepharose and adenosine 2',5'-bisphosphate-Sepharose. Homogeneous enzyme with a subunit Mr of 35 500 is obtained in 35% yield. The Mr of the native enzyme, determined by three different methods, yielded values that suggest that the enzyme is dimeric. NADPH is required as cofactor, and cannot be replaced by NADH. The activity of the purified enzyme towards 2-trans-double bonds in 2-monoene and 2,4-diene structures was investigated. 2-Enoyl-CoA reductase reduced the double bonds in a series of 2-trans-monoenoyl-CoA esters with different chain lengths, but did not exhibit significant activity towards 2-trans-double bonds of 2,4-dienoyl-CoA esters. This result is discussed in the light of analogous observations with enoyl-CoA hydratase.     

Human cationic trypsinogen. Purification, characterization, and characteristics of autoactivation

Human pancreatic cationic trypsinogen has been purified to homogenity from an acetone powder of pancreatic tissue. After an initial ion exchange chromatography step on sulfopropyl (SP)-Sephadex at pH 2.6, cationic trypsinogen was separated from the majority of trypsin activity by passage through an affinity column of lima bean trypsin inhibitor-agarose at high ionic strength. The zymogen was then further purified by affinity chromatography on the same material at low ionic strength. Highly purified trypsinogen was resolved from containing chymotrypsinogen by ion exchange chromatography on SP-Sephadex at pH 6.0. The purified zymogen was shown to be homogeneous by polyacrylamide gel electrophoresis at pH 2.1 and at pH 4.3 as well as by discontinuous sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The autoactivation of human trypsinogen was investigated at pH 5.6 and at pH 8.0. The rate of autoactivation of the human zymogen is rapid at pH 5.6 and is maximal in approximately 1 mM Ca2+. These results are in marked contrast to those previously reported for autoactivation of bovine trypsinogen, which is extremely slow at pH 5.6 and which shows a dependence on at least 50 mM Ca2+ for maximum rate of activation (MacDonald, M. R., AND Kunitz, M. (1941) J. Gen. Physiol. 25, 53-73).     

Active catalytic fragment of Ca2+/calmodulin-dependent protein kinase II. Purification, characterization, and structural analysis.

We report the purification and characterization of an active catalytic fragment of Ca2+/calmodulin-dependent protein kinase II, derived from autophosphorylation and subsequent limited chymotryptic digestion of the purified rat forebrain soluble kinase. The purified fragment was completely Ca2+/calmodulin-independent, existed as a monomer, and phosphorylated synapsin I at the same sites as does the native form of Ca2+/calmodulin-dependent protein kinase II. Kinetic studies with the purified fragment revealed a more than 10-fold increase in Vmax and a 50% decrease in Km for synthetic peptide substrates, compared with native Ca2+/calmodulin-dependent protein kinase II. No 32P-labeled autophosphorylated residues were detected in the purified active fragment, indicating that the autophosphorylation sites were not contained within this fragment. Comparative studies of this active fragment (30 kDa) and its inactive counterpart (32-kDa fragment) revealed certain structural details of both fragments. Calmodulin-overlay study, immunoblot analysis, and direct amino acid sequencing suggest that both fragments contain the entire NH2-terminal catalytic domain and were generated by distinct cleavage within the regulatory domain. The putative cleavage sites for both fragments are discussed.