Neutral lipid storage disease with myopathy and myotonia associated to pathogenic variants on PNPLA2 and CLCN1 genes: case report

BACKGROUND

Neutral lipid storage disease with myopathy (NLSD-M) is an autosomal recessive disease that manifests itself around the 3rd to 4th decade with chronic myopathy predominantly proximal in the shoulder girdle. Clinical myotonia is uncommon. We will report a rare case of association of pathogenic variants on PNPLA2 and CLCN1 genes with a mixed phenotype of NLSD-M and a subclinical form of Thomsen's congenital myotonia.

CASE PRESENTATION

We describe a patient with chronic proximal myopathy, subtle clinical myotonia and electrical myotonia on electromyography (EMG). Serum laboratory analysis disclosure hyperCKemia (CK 1280 mg/dL). A blood smear analysis showed Jordan's anomaly, a hallmark of NLSD-M. A genetic panel was collected using next-generation sequencing (NGS) technique, which identified two pathogenic variants on genes supporting two different diagnosis: NLSD-M and Thomsen congenital myotonia, whose association has not been previously described.

CONCLUSIONS

Although uncommon, it is important to remember the possibility of association of pathogenic variants to explain a specific neuromuscular disease phenotype. The use of a range of complementary methods, including myopathy genetic panels, may be essential to diagnostic definition in such cases.

South American rattlesnake cationic polypeptide crotamine trafficking dynamic in Plasmodium falciparum-infected erythrocytes: Pharmacological inhibitors, parasite cycle and incubation time influences in uptake

Malaria is a parasitic infectious disease caused by Plasmodium sp, which was responsible for about 409 thousand deaths only in 2019. The clinical manifestations in patients with malaria, which may include fever and anemia and that can occasionally lead to the death of the host, are mainly associated to the asexual blood stage of parasite. The discovery of novel compounds active against stages of the intraerythrocytic cell cycle has been the focus of many researches seeking for alternatives to the control of malaria. The antimalarial effect of a native cationic polypeptide from the venom of a South American rattlesnake named crotamine, with ability of targeting and disrupting the acidic compartments of Plasmodium falciparum parasite, was previously described by us. Herein, we extended our previous studies by investigating the internalization and trafficking of crotamine in P. falciparum-infected erythrocytes at different blood-stages of parasites and periods of incubation. In addition, the effects of several pharmacological inhibitors in the uptake of this snake polypeptide with cell-penetrating properties were also assessed, showing that crotamine internalization was dependent on ATP generated via glycolytic pathway. We show here that crotamine uptake is blocked by the glycolysis inhibitor 2- deoxy-D-glucose, and the most efficient internalization is observed at trophozoite stage of parasite after at least 30 min of incubation. The present data provide important insights into biochemical pathway and cellular features determined by the parasite cycle, which may be underlying the internalization and effects of cationic antimalarials as crotamine.

The association of cow-related factors assessed at metritis diagnosis with metritis cure risk, reproductive performance, milk yield, and culling for untreated and ceftiofur-treated dairy cows

Our objective was to assess the association of cow-related factors with metritis cure risk and economically important outcomes. In this prospective cohort study nested inside a randomized clinical trial, cows enrolled in a clinical trial that aimed to evaluate an alternative metritis therapy that had available plasma samples collected at metritis diagnosis were included. Metritis was defined as fetid, watery, reddish-brownish discharge with or without fever, and cure was defined as the absence of metritis signs 12 d after diagnosis. Cows were randomly allocated to remain untreated (CON; n = 147) or receive subcutaneous injections of 6.6 mg/kg of ceftiofur crystalline-free acid at enrollment and 72 h later (CEF, n = 168). Additionally, a random subset of 150 nonmetritic cows (NMET) was also included to compare milk production, reproductive performance, and culling responses. Cow-related factors evaluated include plasma concentrations of nonesterified fatty acids, β-hydroxybutyrate, and haptoglobin (Hp), parity, rectal temperature, and days in milk (DIM) at metritis diagnosis, vulvovaginal laceration (VL), BCS, dystocia, twins, and retained placenta. Among CON cows, DIM at metritis diagnosis was positively associated with metritis cure [threshold = 8, area under the curve (AUC) = 0.67], whereas plasma Hp concentration tended to be negatively associated with cure of metritis (threshold = 0.54 mg/mL, AUC = 0.64). Among CEF cows, DIM at metritis diagnosis (threshold = 5, AUC = 0.67) and dystocia were positively associated with metritis cure, whereas VL and Hp (threshold = 0.78 mg/mL, AUC = 0.76) were negatively associated with cure. For CON cows that were diagnosed with metritis after 8 DIM or had plasma Hp concentration ≤0.54 mg/mL, milk production, pregnancy, and culling risk were comparable to NMET cows. However, performance was impaired when cows that developed metritis at ≤8 DIM or had Hp >0.54 mg/mL were left untreated. Among CEF cows, Hp, DIM at metritis diagnosis, dystocia, and VL were associated with metritis cure. Milk yield, reproductive performance, and culling losses are more pronounced among CEF cows when metritis was diagnosed at ≤5 DIM, Hp >0.78 mg/mL, or if they had VL or dystocia. In conclusion, these data indicate that timing of the onset of metritis and inflammatory biomarkers could be used for the development of a selective therapy strategy for metritis, but more research is needed to identify more accurate predictors of metritis spontaneous cure and treatment failure.

Inhibition of malaria parasite Plasmodium falciparum development by crotamine, a cell penetrating peptide from the snake venom

We show here that crotamine, a polypeptide from the South American rattlesnake venom with cell penetrating and selective anti-fungal and anti-tumoral properties, presents a potent anti-plasmodial activity in culture. Crotamine inhibits the development of the Plasmodium falciparum parasites in a dose-dependent manner [IC50 value of 1.87 μM], and confocal microscopy analysis showed a selective internalization of fluorescent-labeled crotamine into P. falciparum infected erythrocytes, with no detectable fluorescence in uninfected healthy erythrocytes. In addition, similarly to the crotamine cytotoxic effects, the mechanism underlying the anti-plasmodial activity may involve the disruption of parasite acidic compartments H(+) homeostasis. In fact, crotamine promoted a reduction of parasites organelle fluorescence loaded with the lysosomotropic fluorochrome acridine orange, in the same way as previously observed mammalian tumoral cells. Taken together, we show for the first time crotamine not only compromised the metabolism of the P. falciparum, but this toxin also inhibited the parasite growth. Therefore, we suggest this snake polypeptide as a promising lead molecule for the development of potential new molecules, namely peptidomimetics, with selectivity for infected erythrocytes and ability to inhibit the malaria infection by its natural affinity for acid vesicles.

Reactive oxygen species mediate lethality induced by far-UV inEscherichia colicells

The involvement of reactive oxygen species (ROS) in the induction of DNA damage to Escherichia coli cells caused by UVC (254 nm) irradiation was studied. We verified the expression of the soxS gene induced by UVC (254 nm) and its inhibition by sodium azide, a singlet oxygen (1O2) scavenger. Additional results showed that a water-soluble carotenoid (norbixin) protects against the lethal effects of UVC. These results suggest that UVC radiation can also cause ROS-mediated lethality.

Alternative pathways for angiotensin II generation in the cardiovascular system

The classical renin-angiotensin system (RAS) consists of enzymes and peptides that regulate blood pressure and electrolyte and fluid homeostasis. Angiotensin II (Ang II) is one of the most important and extensively studied components of the RAS. The beneficial effects of angiotensin converting enzyme (ACE) inhibitors in the treatment of hypertension and heart failure, among other diseases, are well known. However, it has been reported that patients chronically treated with effective doses of these inhibitors do not show suppression of Ang II formation, suggesting the involvement of pathways alternative to ACE in the generation of Ang II. Moreover, the finding that the concentration of Ang II is preserved in the kidney, heart and lungs of mice with an ACE deletion indicates the important role of alternative pathways under basal conditions to maintain the levels of Ang II. Our group has characterized the serine protease elastase-2 as an alternative pathway for Ang II generation from Ang I in rats. A role for elastase-2 in the cardiovascular system was suggested by studies performed in heart and conductance and resistance vessels of normotensive and spontaneously hypertensive rats. This mini-review will highlight the pharmacological aspects of the RAS, emphasizing the role of elastase-2, an alternative pathway for Ang II generation.

Characterization of a local renin-angiotensin system in rat gingival tissue

BACKGROUND

The systemic renin-angiotensin system (RAS) promotes the plasmatic production of angiotensin (Ang) II, which acts through interaction with specific receptors. There is growing evidence that local systems in various tissues and organs are capable of generating angiotensins independently of circulating RAS. The aims of this study were to investigate the expression and localization of RAS components in rat gingival tissue and evaluate the in vitro production of Ang II and other peptides catalyzed by rat gingival tissue homogenates incubated with different Ang II precursors.

METHODS

Reverse transcription-polymerase chain reaction assessed mRNA expression. Immunohistochemical analysis aimed to detect and localize renin. A standardized fluorimetric method with tripeptide hippuryl-histidyl-leucine was used to measure tissue angiotensin-converting enzyme (ACE) activity, whereas high performance liquid chromatography showed products formed after the incubation of tissue homogenates with Ang I or tetradecapeptide renin substrate (TDP).

RESULTS

mRNA for renin, angiotensinogen, ACE, and Ang II receptors (AT(1a), AT(1b), and AT(2)) was detected in gingival tissue; cultured gingival fibroblasts expressed renin, angiotensinogen, and AT(1a) receptor. Renin was present in the vascular endothelium and was intensely expressed in the epithelial basal layer of periodontally affected gingival tissue. ACE activity was detected (4.95 +/- 0.89 nmol histidyl-leucine/g/minute). When Ang I was used as substrate, Ang 1-9 (0.576 +/- 0.128 nmol/mg/minute), Ang II (0.066 +/- 0.008 nmol/mg/minute), and Ang 1-7 (0.111 +/- 0.017 nmol/mg/minute) were formed, whereas these same peptides (0.139 +/- 0.031, 0.206 +/- 0.046, and 0.039 +/- 0.007 nmol/mg/minute, respectively) and Ang I (0.973 +/- 0.139 nmol/mg/minute) were formed when TDP was the substrate.

CONCLUSION

Local RAS exists in rat gingival tissue and is capable of generating Ang II and other vasoactive peptides in vitro.

Identification of crotasin, a crotamine-related gene of Crotalus durissus terrificus

Crotamine is a cationic peptide (4.9 kDa, pI 9.5) of South American rattlesnake, Crotalus durissus terrificus' venom. Its presence varies according to the subspecies or the geographical locality of a given species. At the genomic level, we observed the presence of 1.8 kb gene, Crt-p1, in crotamine-positive specimens and its absence in crotamine-negative ones. In this work, we described a crotamine-related 2.5 kb gene, crotasin (Cts-p2), isolated from crotamine-negative specimens. Reverse transcription coupled to polymerase chain reaction indicates that Cts-p2 is abundantly expressed in several snake tissues, but scarcely expressed in the venom gland. The genome of crotamine-positive specimen contains both Crt-p1 and Cts-p2 genes. The present data suggest that both crotamine and crotasin have evolved by duplication of a common ancestor gene, and the conservation of their three disulfide bonds indicates that they might adopt the same fold as beta-defensin. The physiological function of the crotasin is not yet known.

Patterns of intracellular cytokines in CD4 and CD8 T cells from patients with mycobacterial infections

Using a short-term bulk culture protocol designed for an intracellular-staining method based on a flow cytometry approach to the frequencies of cytokine-producing cells from tuberculosis and leprosy patients, we found distinct patterns of T cell subset expression. The method also reveals the profile of peak cytokine production and can provide simultaneous information about the phenotype of cytokine-producing cells, providing a reliable assay for monitoring the immunity of these patients. The immune response of Mycobacterium leprae and purified protein derivative (PPD) in vitro to a panel of mycobacteria-infected patients from an endemic area was assessed in primary mononuclear cell cultures. The kinetics and source of the cytokine pattern were measured at the single-cell level. IFN-gamma-, TNF-alpha-, IL-4- and IL-10-secreting T cells were intracytoplasmic evaluated in an attempt to identify M. leprae- and PPD-specific cells directly from the peripheral blood. The analysis by this approach indicated that TNF-alpha was the first (8 h) to be produced, followed by IFN-gamma (16 h), IL-10 (20 h) and IL-4 (24 h), and double-staining experiments confirmed that CD4+ were a greater source of TNF-alpha than of CD8+ T cells (P < 0.05). Both T cell subsets secreted similar amounts of IFN-gamma. We conclude that the protocol permits rapid evaluation of cytokine production by different T cell populations. The method can also be used to define immune status in non-infected and contact individuals.

In vitro-induced antibody production in chronic hepatitis C virus infection

The objectives of the present study were to assess the in vitro-induced anti-hepatitis C virus (HCV) antibody production (IVIAP) in relation to the clinical, biochemical, virologic and histologic variables of patients with HCV infection. The study included 57 patients (60% males) with HCV infection (anti-HCV and HCV-RNA positive). Alanine aminotransferase (ALT) was elevated in 89% of the patients. Mean viral load was 542,241 copies/ml and histology of the liver showed chronic hepatitis in 27/52 (52%) and cirrhosis in 11/52 (21%) patients. IVIAP levels were determined by immunoenzymatic assay at median absorbance of 0.781 at 450 nm. IVIAP was negative in 14% of the patients. When groups with IVIAP levels above and below the median were compared, high IVIAP levels were associated with the male sex, elevated ALT levels and more advanced disease stage. After logistic regression analysis, advanced histologic damage to the liver remained as the only independent variable associated with elevated IVIAP levels. Using a receiver operator characteristic curve, the best cut-off level for IVIAP was established (= 1.540), with 71% sensitivity and 94% specificity for the detection of more advanced disease stages (grades 3 and 4). These findings are consistent with the participation of immunological mechanisms in the genesis of the hepatic lesions induced by HCV and indicate that the IVIAP test may be useful as a noninvasive marker of liver damage either alone or in combination with other markers.

Salivary cortisol for screening of Cushing's syndrome in children

OBJECTIVE

Cushing's syndrome (CS) is characterized by changes in diurnal cortisol variation and total or partial resistance to cortisol suppression by dexamethasone (DEX). Diagnosing CS is a challenge especially in childhood and requires differentiation from primary obesity. The aim was verify the efficacy of salivary cortisol in differentiating primary obesity from CS in children.

SUBJECTS AND METHODS

We studied 11 patients with CS confirmed by standard laboratory investigation and surgical findings aged 1-16 years, and 21 age-matched primary obese controls. Salivary samples were collected at 0900 h, 2300 h, and after an overnight DEX suppression test (20 microg/kg up to 1 mg). Salivary cortisol was measured by RIA.

RESULTS

Diurnal variation of salivary cortisol levels was observed in all controls, as opposed to only 5 of 11 patients with CS. Suppression of salivary cortisol was detected in all controls but in no CS patient after the overnight DEX test. Mean salivary cortisol levels were higher in the CS than in the control group both at 2300 hours and at 0900 hours after DEX but no difference was observed at 0900 hours of the first day. The sensitivity and specificity of salivary cortisol at 0900 h, 2300 hours and after-DEX in diagnosing CS were 27% and 95.2%, 100% and 95. 2%, and 100% and 95.2%, respectively. Sensitivity and specificity of 100% were obtained by combining the data for 2300 hours and after-DEX.

CONCLUSION

The combination of salivary cortisol determination at 2300 hours and after-Dexamethasone is an easily performed and noninvasive method with high specificity and sensitivity for diagnosing Cushing's syndrome in children.

Nucleotide sequence of crotamine isoform precursors from a single South American rattlesnake (Crotalus durissus terrificus)

A cDNA phage library was constructed from venom glands of a single adult specimen of crotamine-plus Crotalus durissus terrificus (South American rattlesnake) captured in a known region. Fifteen crotamine positive clones were isolated using a PCR-based screening protocol and sequenced. These complete cDNAs clones were grouped for maximal alignment into six distinct nucleotide sequences. The crotamine cDNAs, with 340-360 bases, encompass open reading frame of 198 nucleotides with 5' and 3' untranslated regions of variable size, signal peptide sequence, one crotamine isoform message, and putative poly(A+) signal. Of these six different crotamine cDNA precursors, two predict the identical amino acid sequence previously described by Laure (1975), and the other four a crotamine isoform precursor where the Leucine residue at position 19 is replaced by isoleucine by a single base change. On the other hand, nucleotide variation was observed in the 5' and 3' untranslated regions, with one interesting variant containing an 18 base pair deletion at the 5' untranslated region which results in the usual ATG initiator being replaced by the rarely used GUG start codon. Comparison by Northern blot analysis of poly(A+) RNA from venom glands of a crotamine-plus specimen to total and poly(A+) RNA from a crotamine-minus snake indicated that crotamine transcripts were not expressed in the crotamine-minus specimen.

Neutrophils isolated from leprosy patients release TNF-alpha and exhibit accelerated apoptosis in vitro

This study demonstrated that polymorphonuclear neutrophils (PMN) participate in the acute inflammatory response in leprosy as effector cells. Lepromatous patients present intense infiltrate of neutrophils in reactional (ENL) lesions. Circulating PMN of nonreactional patients, healthy donors, and reactional patients were purified and analyzed in vitro. The study confirmed the short lifespan of these cells in culture with progressive changes characteristic of apoptosis. Apoptosis was greatly accelerated in ENL patients as shown by cellular morphology, later confirmed by qualitative and quantitative analysis of fragmented DNA. It was observed that neutrophils stimulated with lipopolysaccharide, Mycobacterium leprae, and lipoarabinomannan secrete interleukin-8 and tumor necrosis factor alpha (TNF-alpha). Thalidomide, a drug known to inhibit TNF-alpha synthesis on monocytes, also exerted an inhibitory effect on TNF-alpha secretion in neutrophils. These data suggest that PMN can participate in the regulation of the immune response in leprosy and can contribute to the amplification of TNF-alpha production at the site of ENL lesion.

Purification and substrate specificity of an angiotensin converting elastase-2 from the rat mesenteric arterial bed perfusate

A soluble angiotensin (Ang) II-generating enzyme has been purified to homogeneity from the rat mesenteric arterial bed (MAB) perfusate by a combination of gel filtration and affinity chromatographies. The enzyme is a glycoprotein of 28.5 kDa (SDS-PAGE), whose N-terminal sequence is identical with that of the rat pancreatic elastase-2; therefore the enzyme will henceforth be referred to as rat MAB elastase-2. When Ang I was used as the substrate, the enzyme specifically released Ang II and the dipeptide His-Leu (Km=36 microM; Kcat=1530 min-1). The catalytic efficiency (Kcat/Km=42.5 min-1 microM-1) of this reaction was comparable to those of other known Ang I-converting enzymes. The proteolytic specificity of the purified enzyme toward mellitin, oxidized insulin B chain, somatostatin-14 and renin substrate tetradecapeptide suggested that the enzyme-substrate interaction was defined by an extended substrate binding site, typical of elastases-2 of pancreatic origin. According to the sensitivity of the rat MAB elastase-2 to various inhibitors this enzyme could be described as a member of the chymostatin-sensitive group of Ang II-forming serine proteases. The localization and biochemical properties of this enzyme suggest that it might play a role in the regional control of vascular tonus.

Distribution and properties of endo-oligopeptidases A and B in the human neuroendocrine system

The thiol activated endo-oligopeptidases A and B were studied in the soluble fraction of human hypothalamus and various endocrine glands. For the identification, characterization and purification of the enzymes, Z-Gly-Pro-NH-Np and bradykinin were used as substrates. Endo-oligopeptidase B showed a molecular mass ranging from 55.5 to 65.5 kDa and isoelectric point from 4.7 to 4.95. Its activity in tissues was highest in the testis, with intermediate levels in the thyroid, neurohypophysis, adenohypophysis and hypothalamus and the lowest activity in the pineal gland. Endo-oligopeptidase A, 467-fold purified by immunoaffinity chromatography, exhibited a molecular mass of 65.5 kDa in the adenohypophysis but 58.5 kDa in other tissues. The isoelectric point ranged from 5.22 to 5.50. High endo-oligopeptidase A activity was observed in the adenohypophysis, testis and hypothalamus with lesser activity in the neurohypophysis and thyroid and the lowest in the pineal gland. Endo-oligopeptidase A cleaved the bonds Phe-Ser of bradykinin, Met-Arg of BAM-12P and Arg-Arg of neurotensin as described for rabbit brain and heart and bovine brain enzymes. This work shows that endo-oligopeptidase A also hydrolysed the bonds Tyr-Gly of LH-releasing hormone, Pro-Phe of angiotensin I and Tyr-Ile of angiotensin II.

Purification and properties of a kininogenin from the venom of Lachesis muta (bushmaster)

An acidic kininogenin from Lachesis muta snake venom was purified to apparent homogeneity by a combination of gel filtration, isoelectric focusing and preparative gel electrophoresis. It was shown to be a highly stable serine protease (mol. wt 27,900; pI 5.4) capable of releasing bradykinin from low mol. wt bovine kininogen and of cleaving some synthetic chromogenic peptides with the following catalytic efficiencies (Kcat/Km, M-1.sec-1): N-benzoyl-Phe-Val-Arg-p-nitroanilide (1.92 x 10(4)); H-D-Val-Leu-Arg-p-nitroanilide (1.55 x 10(4)); N-acetyl-Phe-Arg-p-nitroanilide (3.98 x 10(2)); no hydrolysis was observed with N-benzoyl-Arg-p-nitroanilide. A marked and sustained hypotensive effect was recorded following i.v. injection of purified kininogenin into rats. Tachyphylaxis was observed after repeated i.v. injection of the enzyme, a phenomenon accompanied by a decrease of only 15% in the total circulating rat kininogen. Both the in vivo action and the enzymatic properties of the L. muta kininogenin indicate that this enzyme might be helpful for understanding the kinin-kininogen system.

A survey of vasoactive peptide metabolizing enzymes in the rat mesenteric arterial bed perfusate

We have demonstrated that the isolated perfused rat mesenteric arterial bed (MAB) secretes peptidases capable of metabolizing bradykinin and angiotensin I. The major degradative pathway of bradykinin by enzymes found in the rat MAB perfusate was mediated by carboxypeptidase A-like activity, whereas angiotensin 1 degradation followed two main routes, one attributable to a carboxypeptidase A-like enzyme and the other to an endopeptidase. This latter enzyme seems to be a novel serine peptidase capable of releasing angiotensin II directly from both angiotensin I and renin substrate tetradecapeptide. The rat MAB perfusate was also shown to contain additional endo- and exopeptidases that might play a role in the metabolism of other vasoactive peptides. Our finding that isolated rat MAB secretes peptidases into the perfusion medium indicates that peptide processing within the microvasculature environment may be effected by enzymes besides those normally found in plasma or associated with cell membranes.

Isolation of neurotoxic peptides from the venom of the 'armed' spider Phoneutria nigriventer

Three neurotoxic fractions, lethal to mice, were isolated from the venom of the spider Phoneutria nigriventer, by gel filtration and reverse phase chromatography (Phoneutria toxins 1, 2 and 3). These toxins have mol. wts in the range 6000-9000, and have different amino acid compositions and N-terminal amino acid sequences. The toxins also differ in the lethality and signs they cause in mice after intracerebro-ventricular injection. The median LD50 being respectively for the whole venom, toxins 1, 2 and 3, 47 +/- 5 micrograms, 45 +/- 4 micrograms, 1.7 +/- 0.7 micrograms and 137 +/- 10 micrograms/kg mouse. Toxins 1 and 2 induce excitatory symptoms in mice and toxin 3 a flaccid paralysis with an ED50 of 40 +/- 5 micrograms/kg mouse as measured also by intracerebro-ventricular injection. The presence in the venom of a non-neurotoxic, smooth muscle active peptide is also described.

A selective assay for endooligopeptidase A based on the cleavage of fluorogenic substrate structurally related to enkephalin

A novel quenched fluorescence substrate, QF-ERP7 (Abz-G-G-F-L-R-R-V-EDDn), structurally related to enkephalins, proved to be suitable for assaying the endooligopeptidase A (E.C.3.4.22.19) activity. The enzyme only splits the L-R bond (Km 1.75 microM, Kcat 8.25 s-1), a reaction efficiently blocked by anti-endooligopeptidase A antibodies and by inhibitor and alternative substrates of the enzyme. Evidences based on the action of inhibitors and on the analysis of QF-ERP7 fragments demonstrated that endooligopeptidase A contributes with 100% of the QF-ERP7 cleaving activity found in the cytosol of rabbit brain homogenates and with 85% of that recovered in the membrane fraction. Homologous substrates, Abz-G-G-F-L-R-R-EDDn and Abz-G-G-F-L-R-EDDn, were resistant to hydrolysis. The convenience and sensitivity of the fluorimetric assay based on the QF-ERP7 moiety offers several advantages compared with previously described painstaking procedures for endooligopeptidase A activity measurements, what will certainly contribute to further our understanding of the role of this enzyme on the peptide hormone metabolism.

The purification and amino acid sequence of the lethal neurotoxin Tx1 from the venom of the Brazilian 'armed' spider Phoneutria nigriventer

A lethal neurotoxic polypeptide of Mr 8 kDa was purified from the venom of the South American 'armed' or wandering spider Phoneutria nigriventer by centrifugation, gel filtration on Superose 12, and reverse phase FPLC on columns of Pharmacia PepRPC and ProRPC. The purified neurotoxin Tx1 had an LD50 of 0.05 mg/kg in mice following intracerebroventricular injection. The complete amino acid sequence of the neurotoxin was determined by automated Edman degradation of the native and S-carboxymethylated protein in pulsed liquid and dual phase sequencers, and by the manual DABITC/PITC double coupling method applied to fragments obtained after digestions with the S. aureus V8 protease and trypsin. The neurotoxin Tx1 consists of a single chain of 77 amino acid residues, which contains a high proportion of cysteine. The primary structure showed no homology to other identified spider toxins.

Enkephalin is liberated from metorphamide and dynorphin A1-8 by endo-oligopeptidase A, but not by metalloendopeptidase EC 3.4.24.15

It has been previously reported that both the cysteinyl-endo-oligopeptidase A and the metalloendopeptidase EC 3.4.24.15 are able to generate enkephalin from a number of enkephalin-containing peptides, including dynorphin A1-8. The present study shows that only endo-oligopeptidase A is able to generate [Leu5]enkephalin and [Met5]enkephalin from dynorphin A1-8 and from metorphamide respectively. It is also shown that endo-oligopeptidase A neither hydrolyses the specific EC 3.4.24.15 substrate alpha-N-benzoyl-Gly-Ala-Ala-Phe p-aminobenzoate, nor is inhibited by the specific EC 3.4.24.15 inhibitor N-[1(RS)-carboxy-2-phenylethyl]-alpha-Ala-Ala-Phe p-aminobenzoate.

Liberation of enkephalins from enkephalin-containing peptides by brain endo-oligopeptidase A

Endo-oligopeptidase A, highly purified from the cytosol fraction of bovine brain by immunoaffinity chromatography, has been characterised as a thiol endopeptidase. This enzyme, known to hydrolyse the Phe5-Ser6 bond of bradykinin and the Arg8-Arg9 bond of neurotensin has been shown to produce, by a single cleavage, [Leu]enkephalin or [Met]enkephalin from small enkephalin-containing peptides. Enkephalin formation could be inhibited in a concentration dependent manner by the alternative substrate bradykinin. The optimal substrate size was found to be 8-13 amino acids, with enkephalin the only product released from precursors in which this sequence is immediately followed by a pair of basic residues. However, the specificity constants (kcat/Km) obtained for endo-oligopeptidase A hydrolysis of bradykinin, neurotensin and dynorphin B are of the same order. Taken together, these results indicate that the substrate amino acid sequence is not the only factor determining the cleavage site of this enzyme. Finally, endo-oligopeptidase A and metalloendopeptidase EC 3.4.24.15 are two different enzymes. The latter is not able to liberate enkephalins from metorphamide and dynorphin.

Brain endo-oligopeptidase A, a putative enkephalin converting enzyme

Endo-oligopeptidase A, highly purified from the cytosol fraction of bovine brain by immunoaffinity chromatography, has been characterized as a thiol endopeptidase. This enzyme, known to hydrolyze the Phe5-Ser6 bond of bradykinin and the Arg8-Arg9 bond of neurotensin, has been shown to produce, by a single cleavage, Leu5-enkephalin or Met5-enkephalin from small enkephalin-containing peptides. Enkephalin formation could be inhibited in a concentration-dependent manner by the alternative substrate bradykinin. The optimal substrate size was found to be eight to 13 amino acids, with enkephalin the only product released from precursors in which this sequence is immediately followed by a pair of basic residues. However, the specificity constants (kcat/Km) obtained for endo-oligopeptidase A hydrolysis of bradykinin, neurotensin, and dynorphin B are of the same order, a result indicating that the substrate amino acid sequence is not the only factor determining the cleavage site of this enzyme.

Primary structure of human C-reactive protein

The complete amino acid sequence has been derived for human C-reactive protein (CRP). The protein yielded a unique sequence containing 187 amino acids in a single polypeptide chain. The NH2-terminal residue of CRP is pyrrolidonecarboxylic acid and the COOH terminus is proline. The 2 half-cystine residues at positions 36 and 78 are involved in a disulfide bond. Based on the amino acid composition derived from the sequence data, a minimal molecular weight of 20,946 has been calculated for human CRP. This value agrees well with the molecular weight of 21,500 established by gel filtration of CRP in 5.0 M guanidine Cl (Gotschlich, E.C., and Edelman, G.M. (1965) Proc. Natl. Acad. Sci. U.S.A. 54, 558--566). The primary structure of human CRP has been examined for internal homology and compared to all known proteins whose structures were published before April, 1978 by two computer programs; program SEARCH and program RELATE (Dayhoff, M. O., ed (1976) in Atlas of Protein Sequence and Structure, Vol. 5, Suppl. 2, pp. 3--8, National Biomedical Research Foundation, Silver Spring, MD). The computer analyses showed no significant repeating sequences within the C-reactive protein molecule. This observation seems to rule out the possibility of gene duplication in the evolution of this protein. Distant homologies, which were statistically insignificant, have been noted to the CH2 domain of immunoglobulin G (IgG) and to C3a anaphylotoxin. The homologie noted are insufficient to support a common evolutionary origin of these proteins. No homology region in other heavy chains was observed. It is therefore preferable, at this point in time, to assign CRP and the protein known as 9.5 S alpha-glycoprotein, P component, and Clt to a new super family unrelated to any other proteins investigated. The homology between these proteins was demonstrated previously (Osmand, A.P., Friedenson, B., Gewurz, H., Painter, R.H., Hofmann, T., and Shelton, E. (1977) Proc. Natl. Acad. Sci. U.S.A. 74, 739--743) on the basis of sequence data on approximately 20 NH2-terminal residues of rabbit C-reactive protein, of Clt, and a cyanogen bromide fragment of human CRP.

Primary structure of human C-reactive protein

The complete amino acid sequence of human C-reactive protein has been established. Distant homologies to C3 homology region in the CH2 domain of IgG and to C3a anaphylotoxin have been noted. No homology to other immunoglobulin homology regions or to the same homology region in other heavy chains was observed. The previously reported homologies between rabbit and human C-reactive protein and protein C1t have been extended and strengthened.

Rabbit brain thiol-activated endopeptidase. Hydrolysis of bradykinin and kininogen

A neutral brain endopeptidase which hydrolyzes bradykinin (Arg1-Pro2-Pro3-Gly4-Phe5-Ser6-Pro7-Phe8-Arg9) at the Phe5-Ser6 peptide bond was activated about 10 times by dithiothreitol. The preferential specificity of the enzyme for small peptides was suggested on the basis of the absence of activity toward a bradykinin-related protein such as S-carboxymethylated plasma kininogen.

Isolation of brain endopeptidases: influence of size and sequence of substrates structurally related to bradykinin

Two thiol-activated endopeptidases with pH optima near pH 7.5 were isolated from the supernatant fraction of rabbit brain homogenates by DEAE-cellulose chromatography, gel filtration and isoelectrofocusing. Peptide bond hydrolysis was measured quantitatively by ion-exchange chromatography with an amino acid analyzer. Brain kininase A hydrolyzes the Phe5-Ser6 peptide bond in bradykinin (Bk), Arg1-Pro2-Pro3-Gly4-Phe5-Ser6-Pro7-Phe8-Arg9. It is isoelectric near pH 5.2 and has a molecular weight of approximately 71 000. The enzyme also hydrolyzes the Phe-Ser peptide bond in Lys-Bk, Met-Lys-Bk, des-Arg1-Bk, Lys9-Bk, Pro-Gly-Phe-Ser-Pro-Phe-Arg, and Gly-Pro-Phe-Ser-Pro-Phe-Arg, but does not hydrolyze (0.1%) this bond in des-Phe8-Arg9-Bk. Brain kininase B hydrolyzes the Pro7-Phe8 peptide bond in Bk. It is isoelectric at pH 4.9 and has a molecular weight of approximately 68 000. Brain kininase B also hydrolyzes the Pro-Phe bond in Lys-Bk, Met-Lys-Bk, Lys9-Bk, Ser-Pro-Phe-Arg, and Phe-Ser-Pro-Arg. Pretreatment of denatured kininogen with brain kininase A or B did not reduce the amount of trypsin-releasable Bk from this precursor protein, indicating that the Bk sequence, when part of a large protein, is not a substrate for either enzyme. However, kininase A and B hydrolyze the octadecapeptide Gly-Leu-Met-Lys-Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg-Ser-Val-Gin-Val. The data show that a large part of the C-terminal portion of bradykinin is important for the brain kininase A activity and, for both enzymes, the size of the peptide and presumably the residues adjacent to the scissle bond are important in determining the rate of peptide bond hydrolysis by these endopeptidases.