Lactational exposure to phthalate monoesters among breastfed infants in Italy

Background

Phthalates are chemicals widely used as additives in plastics, cosmetics and medical devices. Due to their endocrine disrupting action and ubiquitous environmental presence, the detection of their levels in breast milk is a crucial public health issue. However, up to date limited information exists on lactational exposure to phthalates in Italy. We aimed to determine the levels of 6 phthalate monoesters in breast milk of women living in Modena (Italy), to investigate the potential sources of exposure and to calculate the Estimated Daily Intake (EDI) for breastfed infants.

Methods

In this cross-sectional study 201 women (19-45 years) living in Modena (Northern Italy) provided a sample of breast milk (30-40 days postpartum) and filled in a questionnaire on personal data and on potential sources of exposure to phthalates. Samples were analyzed by triple Quad LC/MS Mass Spectrometry. Phthalates levels were used to calculate newborns' EDIs that were compared with the Tolerable Daily Intake (TDI) set up by the European Food Safety Authority (EFSA).

Results

Monoethyl phthalate (MEP) and monoisononyl phthalate (MiNP) were detected in most samples, respectively, in 173 (86%; mean: 14.50±80.88; range: 0.03-674 μg/l) and 160 samples (80%; mean: 1.41±2.48; range: 0.04-18.40 μg/l). Levels appeared higher in women more frequently consuming food and beverages preserved in plastic containers or using cosmetics, although differences were not significant. The EDI levels for MEP (mean: 2.08±11.39 µg/kg BW/day) and MiNP (mean: 0.20±0.33 µg/kg BW/day) appeared below the TDI values set up by EFSA.

Conclusions

Although the widespread diffusion of phthalate monoesters in breast milk, their levels resulted lower than those reported in other studies and the EFSA recommended values. Thus, the use of breast milk, a unique nourishment for infants, should not be discouraged.

Key messages

Monitoring phthalates’ levels in breast milk is crucial to check breastfed infants’ exposure and to prevent potential health risks associated with this exposure. It’s essential to adopt effective public health interventions to reduce phthalates dissemination in environment and food and consequently the maternal and infant exposure to these contaminants.

Physical activity during pregnancy in Italy: prevalence, intensity and associated factors

Background

Recently the Italian Ministry of Health, following WHO and ACOG example, recommend that healthy pregnant women practice at least 150 minutes per week of moderate intensity activity (3-6 METs). The study aimed to evaluate if women meet guidelines and to identify potential target groups for public health intervention.

Methods

From November 2015 to November 2017, 390 women completed, just after delivery at an Italian hospital, a questionnaire about sports and exercise before and during pregnancy. Physical activity (PA) was classified according to intensity in Metabolic Equivalent Task (MET). Women were considered sufficiently active when reaching the recommended PA levels.

Results

52% of women practiced any sport at anytime during pregnancy, with a higher prevalence in the II trimester (45%), while only 30% of women kept exercising throughout all trimesters. When including time and sport intensity, only 4,6%, 6,4% and 4,6% of women reached the recommended PA levels in the I, II and III trimester. Sufficiently active women practiced mainly swimming and walking, two highly recommend sports in pregnancy. Factors favour PA practice were Italian nationality, higher educational level, work, BMI, attending birthing classes and being active before pregnancy. However, even without contraindications, 26% of women active before pregnancy stopped exercising in pregnancy and only 15% achieved recommended PA levels. 58% of sedentary women before pregnancy, kept being sedentary in pregnancy.

Conclusions

Although half of women practiced sport during pregnancy, only a few were sufficiently regular and active. As pregnancy is an ideal time to adopt or to reinforce a healthy lifestyle, public health interventions should be strengthen considering also specific target groups.

Key messages

Effective public health policies should be identified and implemented to favour an active lifestyle during pregnancy. Specific target groups less prone to meet PA guidelines should also be addressed.

50 Hz extremely low frequency electromagnetic fields enhance protein carbonyl groups content in cancer cells: effects on proteasomal systems

Electromagnetic fields are an assessed cause of prolonging free radicals lifespan. This study was carried out to investigate the influence of extremely low frequency electromagnetic fields on protein oxidation and on the 20S proteasome functionality, the complex responsible for the degradation of oxidized proteins. Caco 2 cells were exposed, for 24-72 hours, to 1 mT, 50 Hz electromagnetic fields. The treatment induced a time-dependent increase both in cell growth and in protein oxidation, more evident in the presence of TPA, while no changes in cell viability were detected. Exposing the cells to 50 Hz electromagnetic fields caused a global activation of the 20S proteasome catalytic components, particularly evident at 72 hours exposure and in the presence of TPA. The finding that EGCG, a natural antioxidant compound, counteracted the field-related pro-oxidant effects demonstrates that the increased proteasome activity was due to an enhancement in intracellular free radicals.

Flavonoids inhibit the amidolytic activity of human thrombin

The effect of a group of natural flavonoids on human thrombin amidolytic activity was investigated using a spectrophotometric inhibition assay while information on the kinetics and thermodynamics was obtained using optical biosensor techniques. All the flavonoids tested acted as reversible inhibitors, and the quercetin-thrombin complex was found to be most stable at pH=7.5. Docking analysis indicated that quercetin's inhibitory behavior could be related to its planar structure and low steric hindrance, and to its ability to form a critical H-bond with thrombin His57.

Aspirin modulates LPS-induced nitric oxide release in rat glial cells

Nitric oxide and prostaglandins are among the numerous substances released by activated glial cells. The aim of this study was to evaluate the effect of high-level aspirin on iNOS expression in cultured rat glial cells treated with lipopolysaccharide (LPS) as pathological stimulator. Using Western Blotting, we verified that aspirin enhanced LPS-induced iNOS expression and the presence of 15-deoxy-Delta(12,14)-prostaglandin (15d-PGJ2) suppressed this aspirin effect. However, the exposure of LPS-treated glial cells to aspirin resulted in a decrease of NO production. These results suggest that aspirin interferes with the cross-talk of prostaglandins and NO, blocking the endogenous negative control exerted by COX products on iNOS expression. On the other side, aspirin seems to act directly on iNOS reducing its activity, even if it does not completely block NO release by LPS-stimulated glial cells. Then aspirin could maintain homeostatic functions of NO, while it prevents toxic effects, corresponding to high NO concentrations.

Effect of neurotoxic metal ions on the proteolytic activities of the 20S proteasome from bovine brain

The effect of oxidative stress induced by neurotoxic metal ions on the properties of the brain 20S proteasome or multicatalytic proteinase complex (MPC) has been studied. Exposure of the 20S proteasome to increasing amounts of Fe(III), Fe(II), Cu(II) or Zn(II) affects its main hydrolytic activities: trypsin-like (T-L), chymotrypsin-like (ChT-L), peptidylglutamyl-peptide hydrolase (PGPH), branched-chain amino acid preferring (BrAAP) and caseinolytic activities, although in different ways. T-L activity showed gradual activation by both iron ions but inhibition by Cu(II) and Zn(II). ChT-L and PGPH activities were inhibited whereas BrAAP activity was widely activated by all the tested metal salts except for zinc ions. Moreover, the exposure to ferrous salt increased the degradation rate of casein. The functional effects appear to be linked to oxidation-induced modifications, as demonstrated by an increase of carbonyl groups following the exposure to metal ions. In addition, modifications induced by ferrous salt on the catalytic subunits were also supported by western blot analyses performed using anti-X, anti-Y and anti-Z antibodies. The results obtained clearly indicate that metal-catalyzed oxidation strongly affects the functions of the brain 20S proteasome, even though the catalytic subunits seem to be differently influenced by oxidative phenomena.

Interaction of Hsp90 with 20S proteasome: thermodynamic and kinetic characterization

The proteasome and heat shock proteins have been found in the centrosome. The evidence of their copurification reported by several studies suggests that they form stable complex. In addition, Hsp90 is involved in the loading of proteasome-generated antigenic peptides to the class I major histocompatibility complex. In this article, we report a detailed thermodynamic and kinetic characterization of the Hsp90-20S proteasome interaction, using a surface plasmon resonance technique. The modulation exerted by protons in solution has been investigated, and the results have been discussed, taking into account structural motifs characterizing the binding interface between the two macromolecules.

Structure--function relationships in bovine thymus 20S proteasome: a fluorimetric study

The structure--function relationships occurring on the bovine thymus 20S proteasome, which exhibits the features of an immunoproteasome, have been studied. The investigation has been performed, essentially, using a fluorimetric approach, taking advantage either of the sensitivity of the complex to sodium dodecil sulfate and chaotropic agents (urea and guanidine hydrochloride) or of the presence, on the molecule, of a high number of tryptophan residues. The results obtained indicate that the perturbation or the oxidation of these residues affect the catalytic events taking place on the thymus proteasome and that the functional effects determined by SDS and chaotropic agents most likely occur through a series of progressive structural modifications leading to an inactive molecule. The presence of structural intermediates in the proteasome inactivation process suggests that thymus proteasome is a molecule characterized, at the same time, by structural flexibility (modulation of active sites) and structural stability (maintaining of the quaternary structure) in agreement with its crucial role in the cell life cycle.

Different functional modulation by heterotropic ligands (2,3-diphosphoglycerate and chlorides) of the two haemoglobins from fallow-deer (Dama dama)

Two haemoglobin components have been identified and purified from fallow-deer (Dama dama) erythrocytes. They are present in similar amounts and the two tetrameric molecules share the same alpha chain, while two different beta chains are detected in the two components. The beta chains differ by 14 residues, even though they both have 145 amino-acid residues, which account for a molecular mass of 16,023 and 16,064 Da, respectively, while alpha chain has 141 residues, yielding a molecular mass of 15,142 Da. Compared with human Hb, the N-terminal region of both beta chains shows deletion of Val beta 1 and the replacement of His beta 2 by a methionyl residue, a modification which is common to most ruminant haemoglobins. Although both isolated components show a low intrinsic affinity for oxygen, meaningful differences between the two haemoglobins have been found with respect to the effect of heterotropic effectors, such as 2,3-diphosphoglycerate and chloride ions. In view of the high sequence homology between the two components, the different effect of heterotropic ligands has been tentatively correlated to possible localized structural variations between beta chains of the two haemoglobin components.

Isolation and characterization of bovine thymus multicatalytic proteinase complex

The multicatalytic proteinase complex (MPC or proteasome) from bovine thymus was isolated and purified to homogeneity applying a protocol utilizing ion exchange and gel permeation chromatography as major purification tools. The purified complex shows molecular properties that are common for proteasomal molecules (high molecular mass, multisubunit organization, and multiple proteolytic activities) even though a peculiar subunit composition and the presence of specific regulatory mechanisms affecting the assembled proteolytic activities suggest a specialized function for this complex. Thymus proteasome is characterized by the presence of LMP2, LMP7, and LMP10 (MECL1) subunits, which replace the X, Y, and Z subunits. Since a similar complex was previously isolated in bovine spleen, it appears that the proteasomal population containing the LMP subunits is characteristic for organs involved in immune response. Both the thymus and spleen proteasomes are characterized by a marked efficiency in cleaving peptide bonds after branched-chain and aromatic amino acids, indicating that this proteasomal population is most likely involved in intracellular processing of class I antigenic peptides and is an example of an "in vivo" functioning immunoproteasome. However, in spite of several similarities, the complexes isolated from the two lymphoid organs do not show superimposable functional properties, which suggests the presence of organ-specific regulatory mechanisms affecting each of the proteolytic components assembled in the complex.

Multimeric self-assembly equilibria involving the histone-like protein H-NS. A thermodynamic study

The thermodynamic parameters affecting protein-protein multimeric self-assembly equilibria of the histone-like protein H-NS were quantified by "large zone" gel-permeation chromatography. The abundance of the different association states (monomer, dimer, and tetramer) were found to be strictly dependent on the monomeric concentration and affected by physical (temperature) and chemical (cations) parameters. On the basis of the results obtained in this study and the available structural information concerning this protein, a mechanism is proposed to explain the association behavior also in relation to the functional properties of the protein.

Peroxynitrite-mediated oxidation of fibrinogen inhibits clot formation

The clotting activity of human fibrinogen was fully inhibited in vitro by peroxynitrite. The decrease of activity followed an exponential function and the concentration of peroxynitrite needed to inhibit 50% of fibrinogen clotting was 22 microM at 25 degrees C. The oxidative modification(s) induced by the peroxynitrite system (i.e. ONOO-, ONOOH and ONOOH*) appeared specifically to affect fibrin clot formation (through the inhibition of fibrinogen polymerization) since the interaction of peroxynitrite-modified fibrinogen with thrombin appeared to be unaffected. The addition of NaHCO3 decreased the peroxynitrite effect on fibrinogen clotting, suggesting that the reactive species formed by the reaction of CO2 with peroxynitrite are less efficient oxidants of peroxynitrite itself. Similar effects were observed after addition of bilirubin, which also exerted a significant protection against peroxynitrite-mediated modification of fibrinogen.

Isolation and N-terminal sequence of multiple forms of granulins in human urine

Three molecular forms of granulins (also known as epithelins) were isolated, for the first time, in human urine. Their N-terminal sequences, which have also been determined, are identical to those of granulins A and B, previously isolated from human leukocytes, and of granulin F, never isolated before but whose primary structure is known on the basis of the cDNA sequence. The urinary molecules, which show a molecular weight of about 6.5 kDa, are most likely produced by a posttranslational proteolytic processing occurring at the level of the kidney, which appears to be the organ richest in granulin precursor mRNA. The molecular events underlying the precursor processing are unknown, even though the involvement of the protease kallikrein, an enzyme thought to be responsible for the processing of several polypeptidic growth factor precursors, could be hypothesized. Granulins, however, do not show antikallikrein activity. The presence in human urine of isoform F, previously not identified from other human sources, seems to support the hypothesis that mature forms of granulins are generated by an organ-specific precursor processing, on the basis of particular physiological requirements, and to suggest also that this isoform may play "in vivo" an important and specific role in the epithelial cells of the human kidney.

Acid-stable serine proteinase inhibitors in the urine of Alzheimer disease subjects

A comparative study of the levels of acid-stable proteinase inhibitors (kallikrein and trypsin inhibitors) in the urine of healthy and Alzheimer subjects, of both sexes, has been performed. A preliminary characterization of the purified inhibitors indicates that the urinary antitryptic activity is accounted for by the presence of the well known Urinary Trypsin Inhibitor (UTI) while an apparently new molecule appears to be responsible for the antikallikrein activity. The urinary levels of kallikrein inhibitors are very similar in healthy and sick subjects while the levels of trypsin inhibitors appear significatively increased in Alzheimer subjects of both sexes. The data presented here support the hypothesis that unpaired proteolytic processes could be involved in the pathogenesis of Alzheimer's disease and suggest that the levels of urinary acid-stable inhibitors may prove to be useful markers of the disease.

Heterotropic modulation of the protease-inhibitor-recognition process. Cations effect the binding properties of alpha-chymotrypsin

The effect of calcium and lanthanide ions (e.g. terbium) on the binding properties of alpha-chymotrypsin has been studied focussing on the modulation exerted by cations on the interaction of the enzyme with the bovine pancreatic trypsin inhibitor (BPTI or Kunitz inhibitor). The results obtained indicate that the cation binding induces conformational transitions, on the enzyme molecule, which destabilize the enzyme-inhibitor complex formation affecting the interaction of the inhibitor with the secondary specificity site of the proteolytic enzyme. This negative heterotropic effect can be observed only with macromolecular inhibitors (or substrates), displaying an extended interacting surface with the enzyme, and it seems linked to the number of positive charges carried by the cations. Thus, owing to the large conformational changes induced by the binding of trivalent cations, the divalent ones (e.g. calcium) appear to be more suitable for a fine regulation of the enzyme activity. The mutual correlation between inhibitors binding to (and calcium release by) the proteolytic enzymes (and vice versa) could assume an important physiological significance linking parameters, such as calcium concentration and the activity levels of proteolytic enzymes, which are both of great importance for the cell life.

Proteinase inhibitors of the Kunitz family in fallow deer organs: a comparative study

Protein proteinase inhibitors belonging to the Kunitz family have been isolated and characterized in several fallow deer organs. In all the organs studied we found the basic pancreatic trypsin inhibitor (BPTI) while its isoforms, previously isolated and characterized in organs of other ruminant species (bovids and ovids), were absent. In the kidney, in addition to BPTI, active fragments of the inter-alpha-trypsin inhibitor were also isolated. The distribution of Kunitz-type inhibitors in different species of ruminants is compared and discussed on the basis of the expression of their encoding genes.

High-performance liquid chromatographic separation of aprotinin-like inhibitors and their determination in very small amounts

A reversed-phase high-performance liquid chromatographic method for the determination and quantitative recovery of fully active aprotinin (the basic pancreatic trypsin inhibitor or Kunitz inhibitor) and aprotinin-like inhibitors in amounts down to 0.5 micrograms is reported. The method, which allows separation of aprotinin isoinhibitors characterized by small differences in the primary structure with respect to aprotinin itself, appears to be suitable for the quantitation and identification of aprotinin-like inhibitors in human biological fluids, in which they appear to be present at very low levels.

Binding of bovine basic pancreatic trypsin inhibitor (Kunitz) as well as bovine and porcine pancreatic secretory trypsin inhibitor (Kazal) to human cathepsin G: a kinetic and thermodynamic study

The effect of pH and temperature on kinetic and thermodynamic parameters for the binding of the bovine basic pancreatic trypsin inhibitor (Kunitz inhibitor; BPTI) as well as bovine and porcine pancreatic secretory trypsin inhibitor (Kazal inhibitor; bovine and porcine PSTI, respectively) to human cathepsin G (EC 3.4.21.20) has been investigated. The affinity of the macromolecular inhibitors examined for cathepsin G is characterized by an endothermic, entropy-driven, behaviour, and shows the following trend: BPTI > bovine PSTI > porcine PSTI. The affinity difference of BPTI as well as of bovine and porcine PSTI for cathepsin G is mostly accounted for by changes in the values of the apparent dissociation rate constant for the proteinase:inhibitor complex destabilization. On increasing the pH from 4.5 to 9.5 (at 25.0 degrees C), the affinity of BPTI, as well as bovine and porcine PSTI for cathepsin G increases thus reflecting the acidic-pK shift of the His-57 catalytic residue from approximately 6.9 in the free enzyme to approximately 5.0 in the serine proteinase:inhibitor complexes. The BPTI as well as the bovine and porcine PSTI binding properties of cathepsin G have been analyzed in parallel with those of related serine (pro)enzyme/macromolecular inhibitor systems. Considering the known molecular models, the observed binding behaviour of BPTI as well as that of bovine and porcine PSTI to cathepsin G has been related to the inferred stereochemistry of the serine proteinase/inhibitor contact region(s).

Bovine pancreatic trypsin inhibitor and homologous polypeptide inhibitors in nephron cells

Bovine pancreatic trypsin inhibitor (BPTI, aprotinin) is a fifty-eight amino acid polypeptide, which is present together with related molecular isoforms in various bovine organs. In the present study these protease inhibitors were isolated from bovine kidney by affinity chromatography on immobilized trypsin and a subsequent FPLC step. Due to their electrophoretic, structural, and inhibitory properties, the inhibitors were strictly similar to the polypeptides identified previously in other bovine organs. Immunohistochemical experiments showed a widespread localization of these polypeptides in nephron epithelial cells (proximal and distal tubules, loop of Henle, collecting tubules).

Proteinase isoinhibitors from bovine spleen: primary structure of an intermediate in the processing of the precursor

The complete amino acid sequence of the proteinase inhibitor III from bovine spleen is reported. It consists of 62 amino acid residues and is identical to that of spleen inhibitor II (an isoinhibitor of the bovine pancreatic trypsin inhibitor, which shares with the latter 89% of sequence identity), except for four extra residues at the C-terminal side. Inhibitor III appears to be an intermediate in the processing of the putative 100-residue primary expression product, which leads to the mature inhibitor II. These results and those previously obtained for another intermediate, isoinhibitor I, are indicative of the following order for the last steps of the precursor processing inhibitor I----inhibitor III----inhibitor II. The mature protein and the two intermediates isolated have a very similar antiproteolytic activity. However, their in vivo target enzyme(s) are not yet known, as also the target enzyme of the bovine pancreatic trypsin inhibitor is not known. Thus, the available data would indicate that either the three isoinhibitors have a distinct functional role, by inhibiting different target enzymes, or inhibitors I and III are obligatory intermediates for directing the final targeting of the mature, functionally relevant inhibitor II.

Kunitz-type proteinase inhibitors in sheep and ox

1. Four protein proteinase inhibitors, belonging to the Kunitz family, were isolated and purified from several sheep organs. 2. Their structural, functional and immunological properties were determined and compared to those of similar inhibitors purified from bovine organs. 3. The Kunitz-type isoinhibitors appear differently distributed in the two species: BPTI, which is the prevailing form in bovids, is found only in minute amounts in sheep organs. 4. The presence of multiple forms of these inhibitors in sheep is discussed on the basis of the same biosynthetic and post-translational processes proposed for the molecules of bovine origin.

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.

Binding of basic pancreatic trypsin inhibitor and related isoinhibitors to leukocytic elastase. Determination of thermodynamic parameters

The effect of temperature, ionic strength and solvation power of mono- and divalent cations on the interaction of BPTI-like inhibitors with human leukocytic elastase has been determined. The binding process is characterized by a non-linear dependence of the equilibrium association constant on 1/T indicating a thermal transition at temperature values ranging between 20 degrees C and 35 degrees C depending on the solvent. The marked dependence of the thermodynamic parameters (delta H degrees, delta S degrees, delta G degrees) and of the transition temperature on the concentration and nature of the cations present in solution seems to indicate that the transition, probably of conformational nature, is related to removal of water molecules upon enzyme/inhibitor complex formation.

Bovine pancreatic trypsin inhibitor and related isoinhibitors in bovine liver. A biochemical and histochemical study

A Kunitz-type inhibitor family has been biochemically and histochemically characterized in bovine liver. This family includes the well-known pancreatic trypsin inhibitor (BPTI) and three BPTI-related molecular forms (isoinhibitors I, II and III). The purification of the inhibitors was performed by affinity chromatography on immobilized trypsin followed by fast protein liquid chromatography. The inhibitors were identical to those identified previously in bovine spleen and lung. Light immunohistochemical experiments were done by a streptavidin-biotin-peroxidase method using two different immunoglobulin preparations, which selectively discriminated between BPTI and the other isoinhibitors. BPTI-related immunoreactivity was found exclusively at the level of isolated cells, of which many were identified as mast cells by toluidine blue staining. By contrast, isoinhibitor-related immunoreactivity showed a more widespread distribution, including hepatocytes, mast cells and biliary duct epithelial cells. Finally, specific immunoreactivity was also present in plasma. These results suggest that: i) BPTI and related isoinhibitors may be involved in the regulation of the activity of some mast cell proteases, as it happens in other bovine organs (Businaro et al. 1987, 1988); ii) BPTI isoinhibitors, but not BPTI itself, may also control proteolytic activities in hepatic specific structures (hepatocytes and biliary duct epithelial cells).

Production and characterization of monoclonal antibodies against bovine pancreatic trypsin inhibitor

Two monoclonal antibodies (MAbs) have been produced, without the use of a supporting carrier, against bovine basic pancreatic trypsin inhibitor (BPTI or aprotinin), a mini-protein composed of 58 amino acids. Both MAbs obtained were found to be IgM. One of them was purified and further characterized. This MAb (ICI) binds to the immunogen with an association constant of 1.6 X 10(6)M-1 at pH 7.4. Competition experiments with trypsin or inactivated trypsin demonstrate that ICI MAb interacts with BPTI at, or near, the proteinase-binding site. ICI MAb binds, with a much lower association constant (approximately 200M-1), to an isoinhibitor (spleen inhibitor II) which differs from BPTI in seven amino-acids; three of these substitutions are at the active site, in the contact area with the proteinase.

Selective oxidation of methionine residues in Kunitz-type protease inhibitors

Bovine pancreatic trypsin inhibitor (BPTI, also known as aprotinin or Kunitz inhibitor, a mini-protein composed of 58 amino-acid residues, containing a single methionine residue at position 52) has been selectively oxidized by treatment with chloramine T, under mild conditions, to the methionyl sulfoxide derivative. Spleen inhibitor II (SI II, an isoform of BPTI containing two methionine residues at positions 18 and 52) has been oxidized under the same conditions. Oxidation affects the functional properties of the two inhibitors differently: the antiproteolytic activity of BPTI towards bovine trypsin and chymotrypsin, porcine kallikrein and human leukocyte elastase is not changed upon oxidation, while in the oxidized SI II, the affinity for both chymotrypsin and elastase decreases, with respect to the native protein. These results have been directly related to the oxidation of Met18 in SI II, located at the P'3 site in the contact area with the proteases.

Interaction between leukocytic elastase and Kunitz-type inhibitors from bovine spleen

The four Kunitz-type protease inhibitors purified from bovine spleen, which include the basic pancreatic trypsin inhibitor (BPTI), form stable complexes with human leukocytic elastase. The values of the affinity constants of these complexes are similar, in agreement with the great structural similarity of the four inhibitors, but are lower than those measured for the complexes with other serine proteases. Two main factors appear to be responsible for the stability of these complexes, i.e., hydrophobic interactions and ionization phenomena that take place during complex formation. These two factors have been analyzed in terms of the general model previously used for describing the interaction between the serine proteases and their natural inhibitors.

Aprotinin-like isoinhibitors in bovine organs

Previous studies have shown that bovine spleen contains, besides aprotinin (bovine pancreatic trypsin inhibitor, BPTI), three iso-inhibitors (I-III), which are structurally and functionally very similar to BPTI. The primary structure of inhibitors I and II indicates that they are not post-translational products of BPTI, in agreement with independent findings on two homologous genes reported to be present in the bovine genome, which encode BPTI and inhibitors I and II, respectively. A careful reinvestigation on the occurrence of these inhibitors in various bovine organs is presented in this paper, based on their isolation with standard biochemical techniques and on functional and structural studies. All data indicate that the same isoinhibitors found in spleen are also present, besides BPTI, in organs such as lung, liver and pituitary gland, where they were never found before. BPTI and inhibitor II always prevail.

Cellular localization of bovine pancreatic trypsin inhibitor and related molecular forms in bovine lung

In addition to bovine pancreatic trypsin inhibitor (BPTI), three BPTI-related molecular forms (isoinhibitors I, II and III) were isolated from bovine lung by affinity chromatography on immobilized trypsin and subsequently purified by Fast Protein Liquid Chromatography. These inhibitors are identical to the isoinhibitors previously isolated from bovine spleen. Their localization in bovine lung was studied by immunohistochemical techniques, using two different immunoglobulin preparations, selectively recognizing BPTI or the other molecular forms. BPTI-related immunoreactivity was found to be restricted to isolated cells, often identified as mast cells by Toluidine Blue staining. In contrast, isoinhibitor-related immunoreactivity, which also occurs in the mast cells, is present in a number of other cell types. These types include: (i) the smooth muscle cells of different calibre vessels, (ii) the ciliated cells of the bronchial epithelium and the related mucus, and (iii) many cells at alveolar level. Comparison of these data with previous results obtained for bovine spleen suggest multiple physiological roles for these inhibitors.

Primary structure of a protease isoinhibitor from bovine spleen. A possible intermediate in the processing of the primary gene product

Sequence studies on the protease isoinhibitor I isolated from bovine spleen have revealed that it consists of two molecular variants which differ only in the presence of an additional COOH-terminal residue, asparagine, in the less abundant form. The complete amino acid sequence shows that they are composed of 65 or 66 residues and predicts Mr of 7223 or 7338, respectively. The sequences correspond exactly to the 58-residue polypeptide chain of spleen isoinhibitor II plus NH2- and COOH-terminal extensions of 2 and 5 or 6 amino acid residues, respectively. Moreover the entire sequences are located within the 100-residue structure deduced from the mRNA and DNA sequences of the putative precursor. These data support the idea that the molecular variants of isoinhibitor I are either mature proteins with distinct functional roles, or intermediates in the multistage processing of the primary product of gene expression, which eventually leads to the mature protein, i.e. inhibitor II.

Vascular localization of bovine pancreatic trypsin-inhibitor-related molecular forms in bovine spleen

Bovine spleen proteic inhibitors of serine proteases, belonging to the bovine pancreatic trypsin inhibitor (BPTI or aprotinin) family, have been localized, using immunocytochemical techniques, in the smooth muscle cells of some bovine spleen blood vessels. This vascular localization also occurs in a variety of bovine organs and differs from that of BPTI itself which is found exclusively in bovine mast cells, in agreement with previous reports. These data would be in favour of a possible involvement of one or more BPTI-type inhibitors in vascular processes by acting at the level of the smooth muscle cells, the tissue responsible for vasodilation/vasoconstriction events.

Kunitz-type inhibitors in human serum. Identification and characterization

Human serum contains small amounts (approximately 0.1 mg/liter) of two protein protease inhibitors of low molecular weight (approximately 6500) and basic isoelectric point (Kunitz-type). They were purified by affinity chromatography on immobilized trypsin and ion-exchange chromatography in the fast protein liquid chromatography system. Their chemical, immunochemical, and functional properties indicate that the purified inhibitors are highly homologous with the basic pancreatic trypsin inhibitor which is widely distributed in bovids and caprids. Their inhibitory activity toward serine proteases such as plasmin and kallikrein suggests a possible regulatory role in blood clotting and fibrinolysis.

A rapid method for purification of arylsulphatase A from rabbit uterus

The arylsulphatase A from rabbit uterus has been purified with a rapid method using Fast Protein Liquid Chromatography (FPLC). The enzyme is an acid glycoprotein with an apparent molecular weight of 110,000. The enzymatic activity is competitively inhibited by various phosphoesters and various ions such as SO4(2-), PO4(3-) and P2O7(4-).

Characterization of three new Kunitz-type inhibitors from bovine spleen: preparation of specific antibodies

Antibodies to bovine spleen inhibitors I, II and III were elicited and their effect on the antiproteolytic activity of these Kunitz type inhibitors was tested. The immunoglobulins contain antibodies common to the four inhibitors in agreement with the great structural similarity of these antigens. Specific antibodies, which only react with the related inhibitor, were also isolated with the aim of localizing and quantifying these inhibitors "in vivo".

Primary structure and antiproteolytic activity of a Kunitz-type inhibitor from bovine spleen

The amino acid sequence of protease inhibitor II, previously isolated from bovine spleen, has been completely elucidated and reveals a high homology (approximately 90%) with that of bovine pancreatic trypsin inhibitor (BPTI), the well-known Kunitz inhibitor. The secondary and tertiary structure of this new inhibitor appears similar to that of BPTI. Whereas its affinity for bovine trypsin, chymotrypsin, and trypsinogen is almost identical to that of BPTI, the affinity for porcine pancreatic kallikrein is decreased, as expected on the basis of the amino acid substitutions. Analysis of the pH dependence of the affinity constant confirms the previous assignment of the ionizable groups, whose pK values are perturbed on complex formation, to kallikrein and not to the inhibitor molecule.

Fluctuations in arylsulphatase activity in the rabbit endometrium during the sexual cycle

Histochemical and biochemical studies were performed to verify the presence of arylsulphatase A (ASA) and B (ASB) in the rabbit uterus. Fluctuations in the activity of these sulphatases during the sexual cycle were also studied. Some structural and functional properties of purified ASA were determined. The results indicate that arylsulphatases are active in the endometrium during both the estrogenic and progesteronic phases. The activity of ASA was much more intense than that of ASB; it increased during estrus and decreased during the post-ovulatory phase. ASB activity, however, decreased during estrus and increased during the post-ovulatory phase. The significance of these fluctuations is discussed in relation to the action of sexual hormones and physiological substrates of arylsulphatases.

Protease inhibitors from the parasitic worm Parascaris equorum

Two proteic inhibitors (I and II) of serine proteases have been purified from the parasitic worm Parascaris equorum by affinity chromatography on immobilized trypsin followed by preparative electrophoresis. They have an apparent relative molecular mass of 9000 and 7000 as determined by gel filtration, a slightly acid isoelectric point (5.5 and 6.1) and a similar amino acid composition. Both inhibitors lack serine, methionine and tyrosine. They bind bovine trypsin extremely strongly with an association constant, Ka, larger than 10(9) M-1, and form a 1:1 complex with this protease. The Ka values for the binding to bovine chymotrypsin are approximately 3.3 X 10(8) M-1 (inhibitor I) and approximately 2 X 10(6) M-1 (inhibitor II). Inhibitor I interacts also with porcine elastase (Ka approximately 5 X 10(7) M-1), while inhibitor II is inactive towards this enzyme.

Immunochemical studies on the Kunitz type inhibitors from bovine spleen

Specific immunoglobulins for bovine spleen inhibitor IV, which is identical to the basic pancreatic trypsin inhibitor (Kunitz inhibitor) from bovine lung, were purified from the serum of immunized rabbits. Immunological and immunochemical experiments have shown that the four inhibitors previously isolated from bovine spleen are cross-reacting antigens with the anti-inhibitor IV - antiserum; however, part of the antibodies are precipitated by inhibitors I, II and III, whereas the remaining ones are only specific for the antigenic determinants present on the inhibitor IV molecule.

Heterogeneity of the basic pancreatic inhibitor (Kunitz) in various bovine organs

Four protein protease inhibitors (I, II, III, IV) having low molecular weights (10 600-6500) and basic isoelectric points were isolated by affinity chromatography from bovine spleen. Inhibitor IV was identified as the basic pancreatic trypsin inhibitor (Kunitz inhibitor); the presence and distribution of components I, II and III vary in the different bovine organs. Spleen inhibitors I, II, III and IV were purified by ion-exchange chromatography; they form 1:1 complexes with trypsin and inhibit enzymatic activity of trypsin, chymotrypsin and kallikrein. Inhibitors I, II and III contain carbohydrate moieties (7-4%) covalently bound to the polypeptide chain. Specific basic pancreatic trypsin inhibitor antiserum has shown the complete identity between inhibitor IV and the basic pancreatic trypsin inhibitor, while partial cross-reactivity between the basic pancreatic trypsin inhibitor and inhibitors I, II and III can be seen from a double immunodiffusion test.

Properties of trout hemoglobins reconstituted with unnatural hemes

Native globins isolated from trout hemoglobin compoents I and IV have been reconstituted with proto-, meso-, and deuteroheme, and the spectral and functional properties of the reconstituted hemoglobins have been investigated. Equilibrium and kinetic studies allow the following conclusions. (a) The properties of the proto-reconstituted hemoglobins are very similar, or indistinguishable, from those of the native Hb's I and IV. (B) The CO binding kinetics for both proteins were found to be consistent with the equilibrium data: the overall association rate constant increases (and the autocatalytic character of the reaction decreases) in the order proto, meso, deutero. (c) A marked pH dependence of both ligand affinity and cooperativity is maintained in the reconstituted Hb's IV: at pH 6 the fractional saturation with oxygen in air (Root effect) is lower for proto- than for meso- and deutero-Hb IV. The results obtained, including partial photodissociation experiments at different pH values, can be considered, to a first approximation, consistent with the basic features of a simple two-states model.

Effect of drugs on oxidation and precipitation of the isolated chains of human hemoglobin

The paper deals with the action of: primaquine, epinephrine, adrenochrome, acetylphenylhydrazine and sulphanilamide on the autoxidation of the isolated chains from human hemoglobin and on the precipitation which follows. The effect of superoxide dismutase and catalase on the drug induced autoxidation allows the assessment of the possible role of O2 derivatives (notably superoxide or peroxide) in the overall reaction mechanism. It is also shown that primaquine and acetylphenylhydrazine enhance precipitation of the isolated oxidized chains, while epinephrine and adrenochrome display a small inhibitory effect on precipitation. These effects do not involve O2 radicals, but have presumably to be related to a destabilizing (or stabilizing) action of the drugs on the structure of the protein.

Presence of a specific uridine 5'-monophosphate pyrophosphorylase in baker's yeast

Uridine 5'-monophosphate pyrophosphorylase was found to be present in baker's yeast. The enzyme preparation, purified about 30-fold, shows a strict specificity toward uracil and requires Mg++ for its activity.

Decay of oxyperoxidase and oxygen radicals; a possible role for myeloperoxidase

The formation of superoxide anion during the decay of oxyperoxidase to ferric peroxidase was detected by using a spectrophotometric assay based on the use of adrenaline. The finding that peroxidase is a potential source of superoxide suggests a possible role for myeloperoxidase in leucocytes.

Bakers' yeast uridine nucleosidase. Purification, composition, and physical and enzymatic properties

Uridine nucleosidase (EC 3.2.2.3) was purified from commercial bakers' yeast to homogeneity, as judged by a single band observed on polyacrylamide disc gel electrophoresis. The molecular weight of the enzyme, estimated by gel filtration, was approximately 32,500. Polyacrylamide electrophoresis in 0.2% sodium dodecyl sulfate showed the presence of two apparently identical subunits of 17,000 molecular weight. The amino acid composition indicated a large excess of glutamic acid and aspartic acid over other amino acid residues and a very low content of tyrosine and tryptophan. Th SH groups analysis performed with 5,5'-dithiobis (2-nitrobenzoic acid) on thenative protein as well as in the presence of 1% sodium dodecyl sulfate showed the existence of one sulfhydryl group per mole of enzyme. Uridine nucleosidase is active on uridine and 5-methyluridine (ribosylthymine) resulting inactive toward all other pyrimidine and purine nucleosides tested. The Km values for uridine and 5-methyluridine were 0.86 x 10(-3) M and 1.66x10--3M, respectively. The optimal pH is around 7.0. The isoelectric point is 5.1. Among a variety of compounds tested only ribose and glucose 6-phosphate were inhibitory and Ki values were 7.2 mM and 0.19 mM, respectively. Furthermore, ribosylthymine competitively inhibited the hydrolysis of uridine. The type of all inhibitions was competitive and the n' values of the Hill plots were near 1. The effect of temperature on the enzyme activity plotted accoring to Arrhenius gave a value of E = 4740 cal per mole. The enzyme in 100 mM phosphate, pH = 7.0, is stable at 4 degrees for 15 days without any loss of activity.