Eustachian tube symptoms are frequent in chronic rhinosinusitis and respond well to endoscopic sinus surgery.

BACKGROUND: Symptoms of Eustachian tube (ET) dysfunction are seldom assessed in patients with chronic rhinosinusitis (CRS). The Sino-Nasal Outcome Test (SNOT-22) quality-of-life tool includes two questions that specifically screen for symptoms of ET dysfunction (Ear Fullness; Ear Pain). OBJECTIVE: The purpose of this study was to determine the extent to which these ET symptoms were present in patients with CRS, and whether these symptoms respond to endoscopic sinus surgery (ESS). METHODOLOGY: SNOT-22 data collected prospectively at time of recruitment into IRB-approved clinical trials or case-control studies in CRS was pooled to provide a cross section of the frequency and severity of ET dysfunction. When applicable to the trials, the SNOT-22 was repeated at least 3 months following ESS. RESULTS: Five trials rendering 131 patients were available for assessment. The control group comprised of 251 participants from two case-control studies. Ear Fullness of equal/greather than 1 was reported in 80/131 CRS patients compared to 45/251 control patients. Ear Pain of equal/greather than 1 was reported in 39/131 CRS patients compared to 33/251 control patients. Following ESS, mean Ear Fullness and Ear Pain scores decreased to 1.17 and 0.73, respectively. CONCLUSION: Symptoms suggestive of ET dysfunction are frequent in CRS, and for most patients the symptoms will decrease post-ESS to a level comparable with a non-CRS population. Patients whose ET symptoms do not respond to ESS may represent a target population for emerging therapeutic options for ET dysfunction.

Compiling comprehensive national health statistics in a fragmented health information system: lessons learned from Lebanon.

In view of the rapid health transition faced by the country and a highly dominant private sector, the issue of obtaining reliable health statistics is becoming a priority for Lebanon. This paper reviews the process of compiling and disseminating national health statistics from the multitude of public, private and nongovernmental partners in the country. The lessons learned from preparing two editions of the National health statistics report in Lebanon allow identification of some challenges and strengths of the current health information system in Lebanon. The experience emphasizes the need for a close partnership with all stakeholders, an efficient management system, adequate human resources and predefined systems and procedures. The process would benefit from having an interactive website for exchange of data and information among stakeholders and the public. The existence of clear guidelines with consistent definitions and standardized forms would also facilitate the collection and analysis of data.

Glucose-dependent insulinotropic polypeptide has impaired effect on abdominal, subcutaneous adipose tissue metabolism in obese subjects.

OBJECTIVE: Glucose-dependent insulinotropic polypeptide (GIP) appears to have a role in lipid metabolism. Recently, we showed that GIP in combination with hyperinsulinemia and hyperglycemia increases triglyceride uptake in abdominal, subcutaneous adipose tissue in lean humans. It has been suggested that increased GIP secretion in obesity will promote lipid deposition in adipose tissue. In light of the current attempts to employ GIP antagonists in the treatment and prevention of human obesity, the present experiments were performed in order to elucidate whether the adipose tissue lipid metabolism would be enhanced or blunted during a GIP, hyperinsulinemic and hyperglycemic (HI-HG) clamp in obese subjects with either normal glucose tolerance (NGT) or impaired glucose tolerance (IGT). DESIGN: Sixteen obese (BMI>30 kg m(-2)) subjects were divided into two groups, based on their plasma glucose response to an oral glucose challenge: (i) NGT and (ii) IGT. Abdominal, subcutaneous adipose tissue lipid metabolism was studied by conducting measurements of arteriovenous concentrations of metabolites and regional adipose tissue blood flow (ATBF) during GIP (1.5 pmol kg(-1) min(-1)) in combination with a HI-HG clamp. RESULTS: In both groups, ATBF responses were significantly lower than what we have found previously in healthy, lean subjects (P<0.0001). The flow response was significantly lower in the IGT group than in the NGT group (P=0.03). It was not possible to show any increase in the lipid deposition in adipose tissue under the applied experimental conditions and likewise the circulating triglyceride (TAG) concentrations remained constant. CONCLUSION: The applied GIP, HI-HG clamp did not induce any changes in TAG uptake in adipose tissue in obese subjects. This may be due to a blunted increase in ATBF. These experiments therefore suggest that GIP does not have a major role in postprandial lipid metabolism in obese subjects.

Decreased plasma chemerin levels in women with gestational diabetes mellitus.

AIMS: To evaluate fasting and post-prandial serum chemerin levels in pregnant women with and without gestational diabetes, and again following delivery when normal glucose homeostasis is re-established. METHODS: Chemerin levels were measured in serum from nine women with gestational diabetes, and from eight age- and BMI-matched pregnant women with normal glucose tolerance during two meal tests: in the third trimester and 3-4 months post partum. All women with gestational diabetes re-established normal glucose tolerance after delivery. RESULTS: Meal intake did not affect serum chemerin levels. The group with gestational diabetes had lower mean serum chemerin levels during the third trimester compared with the group with normal glucose tolerance (28 ± 1.3 vs. 88 ± 3.5 ng/ml, P < 0.0001). In the group with normal glucose tolerance, mean serum chemerin levels decreased significantly post partum to 57 ± 2.8 ng/ml (P = 0.0001), but remained significantly (P = 0.0003) higher than post-partum levels in the group with gestational diabetes (31 ± 1.9 ng/ml), which did not differ significantly from third trimester levels (P = 0.31). CONCLUSIONS: Normal pregnancy is associated with increased circulating chemerin levels, which may act to reduce pregnancy-induced insulin resistance and prevent glucose intolerance. Women with gestational diabetes, however, have severely reduced chemerin levels that remain low after delivery, which may contribute to the insulin resistance, glucose intolerance and high type 2 diabetes risk associated with gestational diabetes.

SARS-CoV-2 Positivity in Early Infancy: A National Cohort From Saudi Arabia.

Background: Data on SARS-CoV-2 in infants ≤ 90 days are limited with conflicting reports regarding its presentation and outcomes. Methods: We conducted an ambispective cohort study using prospectively collected Health Electronic Surveillance Network Database by the Ministry of Health, Saudi Arabia. Infants of ≤ 90 days of age who had a positive RT-PCR test for SARS-CoV-2 virus were included. Patients were divided in Early neonatal (0-6 days), late neonatal (7-27 days), and post- neonatal (28-90 days) groups and were compared for clinical characteristics and outcomes by contacting parents and collecting information retrospectively. Results: Of 1,793 infants, 898 infants were included for analysis. Most infants in the early neonatal group had no features of infection (tested based on maternal positivity), whereas most infants in the late and post- neonatal groups were tested because of clinical features of infection. Fever and respiratory signs were the most common presenting feature in the late and post-neonatal groups. Hospitalization was higher in the early neonatal group (80%), compared to the two other groups. The overall mortality in the cohort was 1.6%. Conclusion: SARS-CoV-2 infection in infants ≤ 90 days might not be as rare as previously reported. The clinical presentation varies based on age at positive RT-PCR result.

An overview of once-weekly glucagon-like peptide-1 receptor agonists--available efficacy and safety data and perspectives for the future.

Incretin-based therapies, such as the injectable glucagon-like peptide-1 (GLP-1) receptor agonists and orally administered dipeptidyl peptidase-4 (DPP-4) inhibitors, have recently been introduced into clinical practice. At present, the GLP-1 receptor agonists need to be administered once or twice daily. Several once-weekly GLP-1 receptor agonists are in phase 3 development. This review examines the efficacy, safety and perspective for the future of the once-weekly GLP-1 receptor agonists: exenatide once weekly, taspoglutide, albiglutide, LY2189265 and CJC-1134-PC, and compared them to the currently available agonists, exenatide BID and liraglutide QD. A greater reduction in haemoglobin A1c (HbA1c) and fasting plasma glucose was found with the once-weekly GLP-1 receptor agonists compared with exenatide BID, while the effect on postprandial hyperglycaemia was modest with the once-weekly GLP-1 receptor agonist. The reduction in HbA1c was in most studies greater compared to oral antidiabetic drugs and insulin glargine. The reduction in weight did not differ between the short- and long-acting agonists. The gastrointestinal side effects were less with the once-weekly agonists compared with exenatide BID, except for taspoglutide. Antibodies seem to be most frequent with exenatide once weekly, while hypersensitivity has been described in few patients treated with taspoglutide. Injection site reactions differ among the long-acting GLP-1 receptor agonists and are observed more frequently than with exenatide BID and liraglutide. In humans, no signal has been found indicating an association between the once-weekly agonists and C-cell cancer. The cardiovascular safety, durability of glucose control and effect on weight will emerge from several ongoing major long-term trials. The once-weekly GLP-1 receptor analogues are promising candidates for the treatment of type 2 diabetes, although their efficacy may not be superior to once-daily analogue liraglutide.

The epidemiology of tick-borne relapsing fever in Iran during 1997-2006.

BACKGROUND: Tick-borne relapsing fever is an acute febrile and endemic disease in Iran. For many reasons, the incidence of disease is on decrease, however tick-borne relapsing fever is still a health issue in the rural areas for travelers. This study was carried out during 1997-2006 to investigate the tick-borne relapsing fever in Iran. METHODS: Based on a cross-sectional, retrospective and descriptive study in all the provinces, the residents in the endemic areas who were febrile and suspicious to tick-borne relapsing fever were enrolled in the study. Tick-borne relapsing fever is a notifiable disease in Iran and the national communicable disease surveillance data were used through questionnaires. The infectivity of Ornithodoros species to Borrelia also was studied in two highly endemic areas including Hamadan and Qazvin provinces. RESULTS: During 1997-2006, a total of 1415 cases have been reported from the entire country. The highest prevalence was observed in year 2002 with the incidence rate of 0.41/100,000 population. Ardabil province is the first ranked infected area (625 out of 1415), followed by Hamadan, Zanjan, Kurdestan and Qazvin provinces sequentially. The disease is recorded during the whole year but its peak occurs during summer and autumn. There have been 87.6% of the cases recorded from June to November. Forty five percent of the infected cases were male and one third of the patients were under 5 years of age. Fifty four percent of the patients comprise the children under 10 years. Ninety two percent of the cases were living in rural areas where their dwellings were close to animal shelters. They were involved mainly with farming and animal husbandry activities. All the febrile patients with confirmed spirochetes in their blood samples were treated according to a national guideline for tick-borne relapsing fever treatment. Only 7% of the patients were hospitalized and 0.8% of them exhibited the Jarisch-Herxheimer reaction. The study of infectivity of Ornithodoros species to Borrelia revealed that Ornithodoros tholozani was infected with Borrelia persica and Ornithodoros erraticus with Borrelia microti. CONCLUSION: Travelers to the rural areas with high prevalence of the disease should be made aware of the risk of tick-borne relapsing fever and use of appropriate control measures. Communicable disease surveillance including tick-borne relapsing fever should be pursued as well.

Effect of hemin and carbon monoxide releasing molecule (CORM-3) on cGMP in rat penile tissue.

INTRODUCTION: Cyclic guanosine monophosphate (cGMP) levels can be regulated by heme oxygenase-1 and 2 (HO-1 and HO-2)-derived carbon monoxide (CO). AIMS: Assessment of the effect of upregulating CO in rat corpora cavernosa (CC) on cavernous cGMP. METHODS: Three experimental groups were studied: first group (N = 40), short-term HO induction over 2 weeks by injection of intraperitoneal increasing doses of hemin; the second group (N = 40) was subjected to intracavernosal injection of CO donor, CORM-3, or its inactive form (iCORM-3) over 2 weeks; the third group (N = 60) was subdivided into three subgroups: the first one received a combined hemin and CORM-3, the second one received hemin and its inhibitor stannus mesoporphyrin (SnMP), and third one received a combined hemin, CORM-3, and SnMP. MAIN OUTCOME MEASURES: In CC, HO-1 and HO-2 gene expression, Northern blot and Western blot, cGMP levels, and HO enzyme activity. RESULTS: In the first group, maximum induction of HO-1 gene expression, HO enzyme activity, and cGMP occurred with 4-mg hemin dose with a successive increase over 2 weeks. In the second group, CORM-3 increased cGMP by twofold compared with iCORM-3, and also increased HO-1 protein. In the third group, SnMP inhibited the enhancing effect of CORM-3 and HO on erectile signaling molecules; i.e., HO-1 gene, enzyme activity, and cGMP. CONCLUSIONS: CORM-3- or hemin-mediated CO release could increase cavernous tissue cGMP.

Assessment of heme oxygenase-1 (HO-1) activity in the cavernous tissues of sildenafil citrate-treated rats.

AIM: To assess heme oxygenase-1 (HO-1) activity in the cavernous tissue of sildenafil citrate-treated rats. METHODS: One hundred and ninety-two Sprague-Dawley male rats, divided into four equal groups, were investigated. Group 1, the control group, received regular animal chow; group 2 received sildenafil citrate by intragastric tube; group 3 received sildenafil and HO inhibitor (zinc protoporphyrin, ZnPP); and group 4 received sildenafil and nitric oxide synthase (NOS) inhibitor L-nitroarginine methyl ester (L-NAME). Twelve rats from each group were killed after 0.5 h, 1 h, 2 h and 3 h of drug administration. Then HO-1 activity, cGMP levels and NOS enzymatic activity in the cavernous tissues were estimated. RESULTS: In cavernous tissue, HO-1 activity, NOS enzymatic activity and cGMP concentration increased significantly in sildenafil-treated rats compared to other groups throughout the experiment. Rats receiving either HO or NOS inhibitors showed a significant decrease in these parameters. HO-1 cavernous tissue activity and NOS enzymatic activity demonstrated a positive significant correlation with cGMP levels (r = 0.646, r = 0.612 respectively; P < 0.001). CONCLUSION: The actions of PDE5 inhibitor sildenafil citrate in the cavernous tissue are partly mediated through the interdependent relationship between both HO-1 and NOS activities.

The blunted effect of glucose-dependent insulinotropic polypeptide in subcutaneous abdominal adipose tissue in obese subjects is partly reversed by weight loss.

BACKGROUND: Glucose-dependent insulinotropic polypeptide (GIP) appears to have impaired effect on subcutaneous abdominal adipose tissue metabolism in obese subjects. The aim of the present study was to examine whether weight loss may reverse the impaired effect of GIP on subcutaneous abdominal adipose tissue in obese subjects. METHODS: Five obese males participated in a 12-week weight loss program, which consisted of caloric restriction (800 Cal day(-)(1)) followed by 4 weeks of weight-maintenance diet. Before and after weight loss, subcutaneous adipose tissue lipid metabolism was studied by conducting regional measurements of arterio-venous plasma concentrations of metabolites and blood flow (adipose tissue blood flow, ATBF) across a segment of the abdominal adipose tissue in the fasting state and during GIP infusion (1.5 pmol kg(-)(1 )min(-)(1)) in combination with a hyperinsulinemic-hyperglycemic clamp. RESULTS: After weight loss (7.5±0.8 kg), glucose tolerance and insulin sensitivity increased significantly as expected. No significant differences were seen in basal ATBF before (1.3±0.4 ml min(-1) 100 g tissue(-1)) and after weight loss (2.1±0.4 ml min(-1) 100 g tissue)(-1); however, a tendency to increase was seen. After weight loss, GIP infusion increased ATBF significantly (3.2±0.1 ml min(-1) 100 g tissue(-1)) whereas there was no increase before weight loss. Triacylglycerol (TAG) uptake did not change after weight loss. Baseline free fatty acid (FFA) and glycerol output increased significantly after weight loss, P<0.001. During the clamp period, FFA and glycerol output declined significantly, P<0.05, with no differences before and after weight loss. Weight loss increased glucose uptake and decreased FFA/glycerol ratio during the clamp period, P<0.05. CONCLUSIONS: In obese subjects, weight loss, induced by calorie restriction, improves the blunted effect of GIP on subcutaneous abdominal adipose tissue metabolism.

Characterization of a potent platelet aggregation inducer from Cerastes cerastes (Egyptian sand viper) venom.

A potent, proteinaceous inducer of platelet aggregation designated as IVa, has been purified to homogeneity from Cerastes cerastes venom by molecular sieve and ion exchange chromatography. It is composed of 2 subunits with total M(r) of 62,000 as shown by native gel chromatography and chemical cross-linking with disuccinimidyl suberate. It is not clear at the present time whether both subunits are identical gene products, however, both have identical N-terminal sequences for the first 15 amino acids. The protein has a pI above 9.6. IVa (0.1 micrograms/ml) could aggregate platelets up to 80% and was inhibited by p-APMSF, leupeptin, iodoacetamide, protein kinase C inhibitor, phosphatase inhibitor, ATP and PGE1, while it was insensitive to acetylsalicylic acid, ADP scavenger system, protein kinase A inhibitor and hirudin. Protein IVa is a serine proteinase with thrombin-like activity as it hydrolysed thrombin chromogenic substrate CBS 34.47, its aggregatory activity was partially inhibited by monoclonal antibodies against GPIb and the thrombin receptor, as was the thrombin, and its ability to induce intracellular Ca2+ release was blocked by pretreating platelets with thrombin. Unlike thrombin, the IVa protein showed very weak coagulant activity as indicated by plasma recalcification time and fibrinogen clotting time although it could hydrolyse fibrinogen alpha-chains.

Retrovirus-mediated human heme oxygenase-1 (HO-1) gene transfer into rat endothelial cells: the effect of HO-1 inducers on the expression of cytokines.

The present study was conducted to investigate if the mechanism of human heme oxygenase-1 (HO-1) mediated angiogenesis was through the induction of vascular endothelial growth factor (VEGF). Also, the effect of HO-1 on the expression of transforming growth factor beta (TGF-beta),was studied in the presence and absence of HO-1 inducers. Rat lung microvessel endothelial cell line transduced with human HO-1 gene was subjected to cell culture (six separate experiments). mRNA extraction and reverse transcriptase polymerase chain reaction (RT-PCR) experiments, were performed to evaluate the expression of HO-1, VEGF, and TGF-beta in the presence and absence of HO inducers including H(2)O(2), endotoxin and snake venom metalloproteinase with disintegrin like activity(SnMP). ELISA technique was performed to evaluate the levels of the studied growth factors. The results of the study showed over expression of VEGF in endothelial cells transduced with HO-1 compared to control non-transduced endothelial cells. On the other hand, the expression of TGF-beta and its protein level were markedly inhibited in HO-1 transduced endothelial cells compared to control non-transduced cells. Endotoxin and SnMP showed more prominent effect on the expression of VEGF and suppression of TGF-beta in HO-1 transduced endothelial cells, suggesting that their effect is most probably mediated through induction of HO-1.

Mechanism of the anticoagulant, Cerastase F-4, isolated from Cerastes cerastes (Egyptian sand viper) venom.

An anticoagulant enzyme, Cerastase F-4, from the venom of Cerastes cerastes was purified to homogeneity and was characterized (1). In the present report the mode of its fibrinogenolytic and fibrinolytic actions, and its effects on some other blood coagulation factors are described. Cerastes F-4 was shown to readily hydrolyze the alpha A chain of fibrinogen followed by the hydrolysis of the beta B chain. The gamma-chain was relatively resistant to hydrolysis. It also degrades the three chains of fibrin at different rates. The degradation products of the two substrates shown on SDS-polyacrylamide gel were quite different from those produced by plasmin, indicating different sites of cleavage by the enzyme. Using specific chromogenic substrates, Cerastase F-4 seems not to show thrombin-like, plasmin-like, kallikrein-like, antithrombin, or antiplasmin actions. Also, it does not activate prothrombin or plasminogen but degrades both of them slowly. It is concluded that the anticoagulation property of the purified enzyme, Cerastase F-4, is due to its destruction of fibrinogen.

Isolation and characterization of an anticoagulant proteinase, cerastase F-4, from Cerastes cerastes (Egyptian sand viper) venom.

An anticoagulant protease, Cerastase F-4, was isolated from the venom of Cerastes cerastes (Egyptian sand viper) by a combination of gel filtration, ion-exchange chromatography, and HPLC. Homogeneity of the purified anticoagulant was established by discontinuous polyacrylamide disc gel electrophoresis and by isotachophoresis. The anticoagulant enzyme is a single polypeptide chain without subunits having a molecular weight of 22,500. It consists of 28% aspartic acid residues and only 7% are basic amino acids. This agrees well with the fact that the anticoagulant is an acidic protein with an isoelectric point of 5.2. The anticoagulant is a proteolytic enzyme which hydrolyzes casein, fibrinogen and fibrin. The enzyme's optimum activity occurs around 55 degrees C. The anticoagulant showed no phospholipase A activity, low lethal activity, low hemorrhagic and capillary permeability activity, and no myotoxic activity.

Proteolysis in vitro of low and high density lipoproteins in human plasma by Cerastes cerastes (Egyptian sand viper) venom.

Envenomation by snake venoms would be expected to result in proteolysis of plasma proteins as well as of cellular constituents. Incubation of human serum with crude venom from Cerastes cerastes showed that the plasma lipoproteins were a target of this venom. Fractionation of the crude venom by gel filtration revealed that high density lipoprotein (HDL) was susceptible almost exclusively to the highest mol. wt fraction of venom and that proteolysis was due to a metalloprotease. Although HDL was degraded only by this metalloprotease, the low density lipoprotein (LDL) was proteolyzed by both metalloproteases and serine proteases present in several fractions of the venom. Despite extensive degradation, LDL remained intact, as judged by gradient gel electrophoresis. The selectivity of venom fractions may prove useful in the study of lipoprotein structure.

Effects of a cercarial toxin derived from venom of the scorpion Leiurus quinquestriatus on frog skeletal muscle.

Cercarial toxin, a protein purified from Leiurus quinquestriatus venom and toxic to Schistosoma mansoni cercariae, was examined for its effects on frog twitch muscle fibres. In concentrations of 3.4-12 microM the toxin, after a delay of several minutes, produced a slowly developing depolarization of the resting membrane and high frequency miniature endplate potentials associated with spontaneous firing of muscle fibre action potentials and twitching. The action potential duration increased from about 3 to more than 100 msec. In advanced stages of poisoning the amplitude of action potentials decreased while oscillations on the plateau level occurred. Short electrical pulses were followed by repetitive firing of prolonged action potentials, while long stimuli elicited long-lasting action potentials with oscillations on the plateau level. Addition of d-tubocurarine blocked spontaneous sub- and suprathreshold activity. Increasing the Ca concentration of the medium markedly shortened the action potentials and stopped repetitive firing. It is concluded that cercarial toxin interferes with the ionic permeabilities of frog twitch fibres in a way similar to that reported for crude venom or one of its highly toxic fractions in frog nerve.

Low molecular weight factor X activator from Cerastes vipera (Sahara sand viper) venom.

Fraction G from Cerastes vipera venom previously purified on Sephadex G100 was refractionated on DEAE-Sephadex A50 column. A factor X activator was obtained. It had a mol. wt of 12,500 and an isoelectric point of 4.4. It shortened the plasma recalcification time of normal plasma, and plasmas deficient in factors V, VII, VIII, IX, XI and XIII, while it had no effect on plasma deficient in factor X or factor II. It had a serine protease activity and a minimal plasmin activity. PMSF, leupeptin and iodoacetamide exerted a pronounced inhibitory effect on its serine protease activity. Polyantivenin could neutralize the coagulant activity of the activator.

Coagulant component in Cerastes cerastes (Egyptian sand viper) venom.

A coagulant component has been purified from Cerastes cerastes venom, using gel filtration on a Sephadex G 100 (fine) column followed by chromatography on a Bio-Rex 70 column. This compound had a proteolytic effect and could coagulate human plasma deficient in factor VIII or (VIII + IX) with the formation of a firm clot. It could also clot plasma deficient in factor X, but the clot formed was soft and not complete. The compound had no effect on platelet aggregation and was nontoxic. This compound is believed to be primarily a factor X activator, as it could replace factor VIII in hemophilic plasmas.

Purification and characterization of phosphodiesterase (exonuclease) from Cerastes cerastes (Egyptian sand viper) venom.

A venom exonuclease 'phosphodiesterase' (E.C. 3.1.4.1) has been purified from Cerastes cerastes venom by a combination of gel filtration on Sephadex G-100 superfine and ion exchange chromatography on DEAE-Sepharose. The enzyme showed a single band on PAGE and SDS-PAGE and had a molecular weight of 110,000. The final preparation was purified 28 fold. It had no carbohydrate and it did not have protease or 5'-nucleotidase activities. Optimum temperature for enzyme activity was 56 degrees C. The enzyme was rapidly inactivated when pre-incubated above 40 degrees C. Energy of activation (Ea) was calculated to be 0.913. The optimum pH was 9.0. Cysteine, glutathione, dithiothreitol, 2-mercaptoethanol, ADP and AMP inhibited the enzyme. Cysteine caused a non-competitive inhibition, while ADP showed a competitive inhibition. EDTA at a concentration of 0.5 mM caused complete inhibition of the enzyme, which could be reversed by the addition of Ca2+ or Mn2+.

Further characterization of the anticoagulant proteinase, cerastase F-4 from Cerastes cerastes (Egyptian sand viper) venom.

A potent anticoagulant, cerastase F-4, was purified from the venom of Cerastes cerastes. The u.v. absorption spectrum revealed a relatively high tyrosine and low tryptophan content. The molar extension coefficient and E278(0.1%) were 19,400 and 0.84, respectively. The enzyme secondary structure, as studied by circular dichroism, showed 23.6% alpha-helix, 34% beta-sheets, 19% beta-turns and 32.5% random coils. When casein was used as a substrate the optimum pH was 10.0 and the Km was 1.45 g/l. Cerastase F-4 is a metallo-enzyme that contains one mole of Ca2+ and one mole of Zn2+ per mole of protein. It is not affected by phenylmethane sulfonylfluoride or soybean trypsin inhibitor, while it is completely inhibited by 0.5 mM EDTA or ethyleneglycol bis (beta-amino ethylether) N,N,N',N'-tetraacetic acid (EGTA). Ca2+, Mg2+ and Zn2+ partially activated the enzyme under different experimental conditions. Our results suggest that Ca2+ and Zn2+ may play a role in maintaining the structural and catalytic integrity of the enzyme.