Isolation and characterization of a proteinase from white gourd

A proteinase from the sarcocarp of Benincasa cerifera was purified. ItsMW was estimated by two different methods to be about 50000. The maximum activity was found in the alkaline pH region against casein as a substrate. The enzyme was strongly inhibited by di-isopropyl fluorophosphate and not inhibited by EDTA and p-chloromercuribenzoic acid.     

Purification and characterization of rat adipose tissue lipoprotein lipase.

Lipoprotein lipase (EC 3.1.1.34) extracted from adipose tissue of glucose-fed rats with 5 mM-sodium barbital, pH 7.5, containing 20% (v/v) glycerol and 0.1% (v/v) Triton X-100, was partially purified by affinity chromatography on heparin linked to Sepharose 4B. Sodium dodecyl sulphate/polyacrylamide-gel electrophoresis of the partially purified enzyme preparation revealed the presence of two major Coomassie-staining bands (mol.wts. 62 000 and 56 000) as well as a number of minor bands. Treatment of partially purified enzyme with [1,3-3H]di-isopropyl fluorophosphate resulted in the incorporation of radiolabel into the band of mol.wt. 56 000, but not into the band of mol.wt. 62 000. Both the amount of the 56 000-mol.wt. polypeptide and the incorporation of [1,3-3H]di-isopropyl fluorophosphate into this band were greatly reduced in the enzyme preparations isolated from adipose tissue of 48 h-starved rats. whereas the amount of the 62 000-mol.wt. polypeptide was unaffected by starvation. Purification of lipoprotein lipase from adipose tissue of glucose-fed rats was also carried out using affinity chromatography on Sepharose 4B linked to heparin with low affinity for antithrombin-III. This procedure resulted in the presence of a single band of mol.wt. 56 000 on sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. These results suggest that the polypeptide of mol.wt. 56 000 corresponds to the subunit of lipoprotein lipase, whereas the 62 000-mol.wt. polypeptide probably represents antithrombin-III.     

Inhibition of Cytokinin-Induced Adventitious Bud Initiation in Torenia Stem Segments by Inhibitors of Serine Proteases

Application of di-isopropyl fluorophosphate (DFP), a highlysensitive inhibitor for serine enzymes, strongly inhibited cytokinin-inducedadventitious bud initiation in Torenia stem segments culturedin vitro. The inhibitory effect was not evident when DFP wasapplied after 3 days of culture. Amount of DFP-binding proteinsremarkably increased in superficial tissues of explants culturedfor 3 and 4 days on a medium containing benzyladenine. At least14 kinds of DFP-binding polypeptides were detected by SDS-polyacrylamidegel electrophoresis and fluorography. DFP-binding to some ofthese polypeptides was inhibited by a prior treatment with phenylmethylsulfonylfluoride and N-p-tosyl-L-lysine chloromethyl ketone. From theseresults, it was suggested that some serine proteases might berelated with biochemical events occurring during the initialstage of adventitious bud differentiation in Torenia stem segments. (Received May 8, 1984; Accepted July 5, 1984)     

Evidence for tripeptide/H+ co-transport in rabbit renal brush-border membrane vesicles.

L-Phe-L-Pro-L-Ala is a tripeptide which is hydrolysable almost exclusively by dipeptidyl peptidase IV in rabbit renal brush-border membrane vesicles. In order to delineate the mechanism of the transport of an intact tripeptide across the brush-border membrane, we studied the characteristics of the uptake of [3H]Phe-Pro-Ala in membrane vesicles in which the activity of dipeptidylpeptidase IV was completely inhibited by treatment with di-isopropyl fluorophosphate. In these vesicles, uptake of radiolabel from the tripeptide was found to be Na(+)-independent, but was greatly stimulated by an inwardly directed H+ gradient. The H(+)-gradient-dependent radiolabel uptake appeared to be an active process, because the time course of uptake exhibited an overshoot phenomenon. The process was also electrogenic, being stimulated by an inside-negative membrane potential. Under the uptake-measurement conditions there was no detectable hydrolysis of [3H]Phe-Pro-Ala in the incubation medium when di-isopropyl fluorophosphate-treated membrane vesicles were used. Analysis of intravesicular contents revealed that the radiolabel inside the vesicles was predominantly (greater than 90%) in the form of intact tripeptide. These data indicate that the uptake of radiolabel from [3H]Phe-Pro-Ala in the presence of an inwardly directed H+ gradient represents almost exclusively uptake of intact tripeptide. Uphill transport of the tripeptide was also demonstrable in the presence of an inwardly directed Na+ or K+ gradient, but only if nigericin was added to the medium. Under these conditions, nigericin, an ionophore for Na+, K+ and H+, was expected to generate a transmembrane H+ gradient. Uptake of Phe-Pro-Ala in the presence of a H+ gradient was inhibited by di- and tri-peptides, but not by free amino acids. It is concluded that tripeptide/H+ co-transport is the mechanism of Phe-Pro-Ala uptake in rabbit renal brush-border membrane vesicles.     

A phosphorylation site in brain and the delayed neurotoxic effect of some organophosphorus compounds

1. It is proposed that part of a neurotoxic dose of di-isopropyl phosphorofluoridate will be covalently bound in vivo to a specific component in the brain and spinal cord as the initial biochemical event in the genesis of the lesion. 2. A test system in vitro was devised that removes many di-isopropyl phosphorofluoridate-binding sites and indicates that the specific component may be a protein present in brain at a concentration comparable with that of the cholinesterases. 3. The site was found to be present and capable of binding di-isopropyl phosphorofluoridate in vitro in brain samples taken from either normal hens or those dosed with organophosphorus esterase inhibitors that are not neurotoxic. 4. Very little of the specific binding activity was found in brain samples from hens pre-dosed with a variety of neurotoxic organophosphorus compounds. 5. A solubilized preparation of the active brain component was obtained, suitable for further purification and study.     

Influence of pulsing and postpulsing media tonicity on electrotransformation of intact yeast cells

Abstract The carboxylesterases from Proteus vulgaris, Salmonella enterica and Citrobacter amalonaticus were purified 104-, 95- and 120-fold, respectively by chromatography. The enzymes had similar catalytic activities but differed considerably in their inactivation by heat, di-isopropyl fluorophosphate and Cd²⁺, Zn²⁺, Hg²⁺ and Cu²⁺. Quantitative neutralization of hydrolytic activity with specific immunoglobulins indicated that the three enzymes were antigenically distinct.     

Inhibition of lipoprotein-associated phospholipase A2 diminishes the death-inducing effects of oxidised LDL on human monocyte-macrophages

The death of macrophages contributes to atheroma formation. Oxidation renders low-density lipoprotein (LDL) cytotoxic to human monocyte-macrophages. Lipoprotein-associated phospholipase A2 (Lp-PLA2), also termed platelet-activating factor acetylhydrolase, hydrolyses oxidised phospholipids. Inhibition of Lp-PLA2 by diisopropyl fluorophosphate or Pefabloc (broad-spectrum serine esterase/protease inhibitors), or SB222657 (a specific inhibitor of Lp-PLA2) did not prevent LDL oxidation, but diminished the ensuing toxicity and apoptosis induction when the LDL was oxidised, and inhibited the rise in lysophosphatidylcholine levels that occurred in the inhibitors' absence. Hydrolysis products of oxidised phospholipids thus account for over a third of the cytotoxic and apoptosis-inducing effects of oxidised LDL on macrophages.     

Characterization of [3H]di-isopropyl phosphorofluoridate-binding proteins in hen brain. Rates of phosphorylation and sensitivity to neurotoxic and non-neurotoxic organophosphorus compounds.

The experiments described in this paper were designed to isolate [3H]di-isopropyl phosphorofluoridate-binding proteins by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis for the purpose of characterizing and identifying potential initiation sites for organophosphorus-compound-induced delayed neurotoxicity. The major Paraoxon-insensitive Mipafox-sensitive binding protein (Mr 160 000) was found to be identical with one previously identified as neurotoxic esterase, an enzyme that has been proposed to be the target site for organophosphorus-compound-induced delayed neurotoxicity. However, two other binding proteins with suitable binding characteristics were also found in smaller amounts, one of which has not been detected previously. Di-isopropyl phosphorofluoridate was found to phosphorylate all three of these proteins at rates similar to the rate at which neurotoxic esterase is inhibited by di-isopropyl phosphorofluoridate. Varying the concentration of di-isopropyl phosphorofluoridate or the time of incubation produced similar increases in binding to each of the labelled proteins. This suggests that the reaction rates of di-isopropyl phosphorofluoridate with proteins may be described by first-order kinetics, and the concentration of the Michael is complex formed during binding is minimal for all the phosphorylated proteins. The recovery of the binding activity in the 160 000-Mr band was found to be similar to the recovery of neurotoxic esterase activity, lending further support to the contention that this band is identical with neurotoxic esterase.     

Purification and properties of esterases characteristic of adult rat brain

1. A method for the partial purification of an esterase fraction, present in the brain of the adult but not the newborn rat, is described. A 54-fold purification was achieved in three steps. 2. When subjected to starch-gel electrophoresis, the purified fraction resolved into three bands of esterase activity. Two of these bands migrate close together and faster than other esterases in the brain. These two esterases are inhibited by p-hydroxymercuribenzoate but not by di-isopropyl phosphorofluoridate. The third band is di-isopropyl phosphorofluoridate-sensitive and migrates just behind the two leading esterases. 3. After treatment with di-isopropyl phosphorofluoridate, to obviate the effects of the di-isopropyl phosphorofluoridate-sensitive esterase, the enzyme preparation hydrolyses alpha-naphthyl acetate, alpha-naphthyl propionate and alpha-naphthyl butyrate, but not cholesteryl acetate. The V(max.) for the naphthyl esters decreased with increase in chain length of the acyl group. The acetate ester is hydrolysed 34 times as fast as the butyrate and about seven times as fast as the propionate derivative. The K(m) values for these three esters, measured at pH7.2 and 37 degrees , are 2.8x10(-4)m, 3.1x10(-4)m and 7.3x10(-5)m for the acetate, propionate and butyrate derivatives respectively. 4. The Hofstee (1952) plots for the kinetic data show a single line, indicating that the two most-rapidly migrating esterases, although electrophoretically separable, are not kinetically distinguishable in the substrate ranges examined.     

Epidemiological typing of Acinetobacter strains by esterase electrophoresis

Fifty-three strains of Acinetobacter, belonging to the species A baumannii, A. haemolyticus and A. johnsonii, were differentiated by electrophoretic typing of their esterases, on the basis of both the enzyme specific activity profiles and their electrophoretic mobilities. Each esterase was defined by its spectrum of hydrolytic activity toward five synthetic substrates and its sensitivity to di-isopropyl fluorophosphate. Since each enzyme was not detected in all strains of a given species, several zymotypes could be defined by the patterns of combinations of esterases. Thus, 24 zymotypes were defined in the 32 A. baumannii strains, 4 were defined in the 10 A. haemolyticus strains and 6 were defined in the 11 A. johnsonii strains. When the electrophoretic mobilities of the various esterases were included, each of the 53 strains of Acinetobacter (with the exception of three A. haemolyticus strains) showed a distinct electrotype.     

Rapid aging of neurotoxic esterase after inhibition by di-isopropyl phosphorofluoridate

1. It was proposed [Johnson (1974) J. Neurochem.23, 785-789] that an essential step in the genesis of delayed neuropathy caused by some organophosphorus esters was aging of phosphorylated neurotoxic esterase, involving generation of a charged monosubstituted phosphoric acid residue on the protein. 2. Neurotoxic esterase of hen brain was inhibited with di-isopropyl phosphorofluoridate either unlabelled or mixed-labelled with (3)H and (32)P. 3. Reactivation of inhibited enzyme by KF was possible only immediately after a brief inhibition:aging at pH8.0 and 37 degrees C occurred with a half-life of about 2-4min. 4. When the radiolabelled enzyme was studied no loss of label was observed during the expected aging period, but a change in the nature of the bound radioisotopes occurred (half-life=3.25min). 5. Alkaline hydrolysis of labelled enzyme liberated di-isopropyl phosphate at early times after labelling, but increasing amounts of monoisopropyl phosphate plus a volatile tritiated compound (possibly propan-2-ol) at later times. 6. Treatment of labelled enzyme with KF released di-isopropyl phosphate and caused reactivation of enzyme to similar degrees. It is concluded that the chemical change from di-isopropyl phosphoryl-enzyme to mono-isopropyl phosphoryl-enzyme and the loss of reactivatibility are related. 7. The rate of aging is similar at pH5.2, 6.5 and 8. Aging is unaffected by addition of reduced glutathione and imidazole at pH5.2 or 8, and none of the transferred (3)H is trapped by these reagents. The mechanism of aging must be different from the better-known dealkylation aging of the cholinesterases.     

The specificity of proteinases from Streptomyces griseus (pronase)

Purification of pronase by ion-exchange chromatography gave four proteolytically active fractions. Fraction A(2) contained an endopeptidase that attacks poly l-valine. Fraction B contained an endopeptidase, an aminopeptidase and carboxypeptidases. The activities against hippuryl-l-arginine and hippuryl-l-phenylalanine could be inhibited to a considerable extent by di-isopropyl phosphorofluoridate and by EDTA. Fraction C contained an endopeptidase resembling bovine trypsin. The pure enzyme was completely inactivated by di-isopropyl phosphorofluoridate and pancreatic trypsin inhibitor and to about 90% by other naturally occurring trypsin inhibitors. Fraction D contained an apparently homogeneous endopeptidase, inhibited by diisopropyl phosphorofluoridate, that adsorbed to and hydrolysed elastin. The activity of all these fractions was tested qualitatively against a wide range of small peptides and synthetic substrates.     

Identification, purification, and localization of tissue kallikrein in rat heart.

A tissue kallikrein has been isolated from rat heart extracts by DEAE-Sepharose and aprotinin-affinity column chromatography. The purified cardiac enzyme has both N-tosyl-L-arginine methyl ester esterolytic and kinin-releasing activities, and displays parallelism with standard curves in a kallikrein radioimmunoassay, indicating it to have immunological identity with tissue kallikrein. The enzyme is inhibited by aprotinin, antipain, leupeptin and by high concentrations of soybean trypsin inhibitor, but stimulated by lima-bean or ovomucoid trypsin inhibitor and low concentrations of soybean trypsin inhibitor. By using a specific monoclonal antibody to tissue kallikrein in Western blot as well as active-site labelling with [14C]di-isopropyl fluorophosphate, the cardiac enzyme was identified as a protein of 38 kDa, a molecular mass identical with that of tissue kallikrein. Immunocytochemistry at the electron-microscopic level localized this enzyme to the sarcoplasmic reticulum and granules of rat atrial myocytes. Two cardiac kallikrein precursors, (38 and 40 kDa) were identified from the translation in vitro of heart mRNA by immunoprecipitation and electrophoresis of [35S]methionine-labelled cell-free translation products. Kallikrein mRNA in the rat heart was also demonstrated by dot-blot analysis using a tissue kallikrein cDNA probe. These results indicate that the tissue kallikrein gene is expressed in the rat heart and that the purified enzyme is indistinguishable from tissue kallikrein with respect to enzymic and immunological characteristics.     

Pancreatic bile salt dependent lipase from cod (Gadus morhua): purification and properties.

The enzymatic basis for cod digestive lipolysis has been investigated. Lipase activity was found in aqueous extracts from pyloric caeca as well as in pancreatic tissue surrounding the caeca and the bile duct. A bile salt-dependent lipase (BSDL) was purified from either defatted powder of cod pyloric caeca or aqueous pancreatic extracts by combined affinity chromatography on cholate-Sepharose and gel filtration on Sephacryl S-200 HR. By SDS-PAGE analysis the molecular weight of purified cod BSDL was estimated to 60 kDa. The enzyme was totally dependent on bile salts for hydrolysis of insoluble fatty acid esters. Antiserum raised against purified cod BSDL reacted specifically with selected mammalian pancreatic BSDLs by Western blot analysis. Results presented in this paper strongly suggest that the bile salt-dependent lipase is the only pancreatic enzyme involved in lipid digestion in cod. The enzyme has been characterized and compared to human pancreatic BSDL with respect to substrate specificity, temperature- and pH-dependence and inhibitors. Both soluble and insoluble fatty acid esters were hydrolysed and the enzyme was 1,3-specific in hydrolysis of triolein. The enzyme was inhibited by di-isopropyl fluorophosphate and phenyl boronic acid, but not significantly by phenyl methyl sulfonyl fluoride. The cod BSDL is probably homologous to mammalian pancreatic BSDLs.     

Radiochemical determination of a unique sequence around the reactive serine residue of a di-isopropyl phosphorofluoridate-sensitive plant carboxypeptidase and a yeast peptidase

Phaseolain, a carboxypeptidase from French-bean leaves, and a partially purified peptidase from baker's yeast are inhibited by reaction with di-isopropyl phosphorofluoridate. Radioactive di-isopropyl [(32)P]phosphorofluoridate was used to show that the site of reaction is a unique serine residue and that the sequence of amino acids adjacent to the reactive serine is Glu-Ser-Tyr. This sequence is different from those of other ;serine' enzymes previously reported and, for phaseolain, represents an unequivocal example of a ;serine' carboxypeptidase.     

Purification of the proteinase from group B streptococci that inactivates human C5a

We previously reported that group B streptococci (GBS) possess a cell-associated activity that inactivates the chemotactic activity generated in zymosan-activated serum by cleaving a specific site within the carboxy termini of C5a and C5adesarg. This inactivates the major chemoattractants for neutrophils that are generated when serum complement is activated. We now report the isolation of the enzyme responsible for the proteolytic cleavage of C5a. Treatment of GBS with mutanolysin, an endo-N-acetyl muramidase, released activity from GBS which destroyed the functional activity of C5a. The soluble activity was purified to homogeneity by hydroxyapatite, ion-exchange and gel-filtration chromatography. Analysis by SDS-PAGE showed that the enzyme (GBS C5a-ase) has an Mr of approx. 120,000. The GBS C5a-ase appears to be a serine esterase on the basis of its sensitivity to di-isopropyl fluorophosphate. This enzyme is distinct from the C5a-cleaving enzyme produced by group A streptococci, since the two bacterial products migrate differently on SDS-PAGE, and lack antigenic cross reactivity. This enzyme may play a role in the pathogenesis of group B streptococcal disease through its ability to rapidly inactivate the potent neutrophil agonist, C5a, at sites of infection.     

The number of acetylcholinesterase molecules in the rat megakaryocyte.

A megakaryocyte cell series from rat bone marrow has been examined by the isotopic di-isopropyl fluorophosphate (DFP) method for esterases. After complete reaction with 32P-DFP, the numbers of DFP-reacted molecules inindividual cells havebeen determined by beta trackauto-radiography. Previous work has shown the percentage of organophosphate-sensitive sites in these cells which can be taken as active centers of acetylcholinesterase (AChase). Combining these data, the absolute numbers of organophosphate-sensitive esterase molecules and AChase molecules per cell were determined. Histograms show a narrow spread of values within each of four size classes from megakaryoblast to fully mature megakaryocyte, but, with means increasing 4-fold through this series, approximately in proportion to cell volume. A rat megakaryoblast has 2 X 10(6) AChase molecules, and a megakaryocyte (of 48-micro diameter) has 7.6 X 10(6) molecules. The apparent turnover number of the enzyme for intracellular reaction with substrate is calculated and compared with turnover numbers available for other AChases.     

Characterization of a high-molecular-weight form of human acrosin. Comparison with human pancreatic trypsin.

A high-molecular-weight form of acrosin (alpha-acrosin, EC 3.4.21.10) was extracted from spermatozoa obtained from frozen semen and purified over 300-fold. Purification was effected by sequential use of Sephadex G-150, CM-cellulose and DEAE-cellulose chromatography. Properties of human acrosin were compared with those of human pancreatic trypsin. The molecular weight (Mr) of acrosin (70000) was greater than that of trypsin (Mr 21000). Isoelectric points for acrosin (pI = 9.0) and trypsin (pI = 8.2) were also different. alpha-N-Benzoyl-L-arginine ethyl ester was hydrolysed 50% more rapidly by acrosin than by trypsin. Acrosin had similar kcat. values for the hydrolysis of esters with different acylating groups (i.e. benzoyl-L-arginine and p-tosyl-L-arginine esters). In contrast, trypsin had dissimilar kcat. values for the hydrolysis of esters with different acylating groups. Kinetic data argue against deacylation as the rate-limiting step in ester hydrolysis by acrosin. Acrosin was less sensitive than trypsin to inhibition by 7-amino-1-chloro-3-L-tosylamidoheptan-2-one ('TLCK'), di-isopropyl fluorophosphate and soya-bean trypsin inhibitor. D-Fructose and D-arabinose inhibited acrosin, but had no effect on trypsin. The data indicate that definite differences exist between human acrosin and trypsin.     

Mast cell tryptase from pig lungs triggers infection by pneumotropic Sendai and influenza A viruses. Purification and characterization.

A novel trypsin-type serine proteinase, which processes the precursors of the envelope fusion glycoproteins of pneumotropic Sendai and human influenza A viruses, was purified to homogeneity from pig lungs. On SDS/PAGE, the purified enzyme gave a protein band corresponding to about 32 kDa, and has an apparent molecular mass of 120 kDa, as determined by gel permeation chromatography. Immunohistochemical staining with antibodies against this enzyme revealed that the enzyme is located in pig lung mast cells. The N-terminal 44-amino-acid sequence of the enzyme exhibits about 80% identity with those of mast cell tryptases from other species. Of the inhibitors tested, di-isopropyl fluorophosphate, antipain, leupeptin, benzamidine and a few proteinaceous inhibitors, such as mucus protease inhibitor and aprotinin, inhibited this enzyme activity. Heparin stabilized the enzyme, but high-ionic-strength conditions did not, unlike for human mast cell tryptase. The purified enzyme efficiently processed the fusion glycoprotein precursor of Sendai virus and slowly processed hemagglutinin of human influenza A virus, and triggered the infectivity of Sendai virus in a dose-dependent manner, although human mast cell tryptase beta and rat mast cell tryptase (rat MCP-7) from lungs did not process these fusion glycoproteins at all. These results suggest that mast cell tryptase in pig lungs is the possible trigger of the pneumotropic virus infections.     

Comparative studies on superoxide anion production by polymorphonuclear leukocytes stimulated with various agents

Guinea-pig peritoneal polymorphonuclear leukocytes promoted superoxide anion (O2(-)) generation when stimulated with soluble antigen-antibody complex, concanavalin A or sodium dodecyl sulfate. The enhancement with antigen-antibody complex or concanavalin A was inhibited with diisopropyl fluorophosphate. On the other hand, the enhancement with sodium dodecyl sulfate was not affected by the inhibitor. L-1-pTosylamido-2-phenylethyl chloromethyl ketone (Tos-PheCH2Cl) and tetrahydrofuran also enhanced O2(-) generation even in the presence of diisopropyl fluorophosphate, while at low concentrations they inhibited O2(-) generation with antigen-antibody complex. These results indicate that a certain diisopropyl fluorophosphate-sensitive factor may be involved in the O2(-)-generating response of leukocytes to antigen-antibody complexes or concanavalin A, but not in that to sodium dodecyl sulfate, Tos-PheCH2Cl or tetrahydrofuran.