Assessing proteases and enzymes of the trypanothione system in subpopulations of Leishmania (Viannia) braziliensis Thor strain during macrophage infection

BACKGROUND Leishmania (Viannia) braziliensis Thor strain exhibits a heterogeneous composition comprised of subpopulations with varying levels of infectivity. Clonal subpopulations were previously obtained from the strain Thor by sorting single-parasites and proceeding cultivation. The subpopulations used in this study are named Thor03, Thor 10 and Thor22. OBJECTIVES Phenotypic characteristics of the parasite, specially focusing on virulence factors and resistance to the antimicrobial mechanisms of macrophages, were investigate in these subpopulations. METHODS Cellular and molecular biology, as well as biochemistry approaches were applied to obtain the data analysed in this study. FINDINGS Relative quantification of gene expression was measured for calpain, cysteine protease B (CPB), and subtilisin proteases but no significant differences in these genes' expression among subpopulations was observed. However, subtilisin and CPB proteins were assessed as more abundant in Thor03 by fluorescence-labelled flow cytometry technique. Western Blotting assays, as semi-quantitative analysis in gel, showed higher concentrations of subtilisin (110 to 50 kDa) and CPB (40 to 18 kDa) in extract of intracellular amastigotes from subpopulations Thor03 and Thor10 and calpain (60 to 25 kDa) showed no significant differences among subpopulations. Complementary, higher trypanothione reductase activity was observed in Thor10 intracellular amastigotes and assays of susceptibility to hydrogen peroxide-inducing agents and nitric oxide donors conducted with promastigotes revealed greater resistance to in vitro oxidative stress induction for Thor10, followed by Thor03. MAIN CONCLUSIONS The data obtained for the virulence factors explored here suggest how multiple coexisting phenotypic-distinct subpopulations may contribute in adaptability of a single L. (V.) braziliensis strain during infection in the host cells.

Brown spider venom toxins: what are the functions of astacins, serine proteases, hyaluronidases, allergens, TCTP, serpins and knottins?

Accidents caused by the bites of brown spiders (Loxosceles) generate a clinical condition that often includes a threatening necrotic skin lesion near the bite site along with a remarkable inflammatory response. Systemic disorders such as hemolysis, thrombocytopenia, and acute renal failure may occur, but are much less frequent than the local damage. It is already known that phospholipases D, highly expressed toxins in Loxosceles venom, can induce most of these injuries. However, this spider venom has a great range of toxins that probably act synergistically to enhance toxicity. The other protein classes remain poorly explored due to the difficulty in obtaining sufficient amounts of them for a thorough investigation. They include astacins (metalloproteases), serine proteases, knottins, translationally controlled tumor proteins (TCTP), hyaluronidases, allergens and serpins. It has already been shown that some of them, according to their characteristics, may participate to some extent in the development of loxoscelism. In addition, all of these toxins present potential application in several areas. The present review article summarizes information regarding some functional aspects of the protein classes listed above, discusses the directions that could be taken to materialize a comprehensive investigation on each of these toxins as well as highlights the importance of exploring the full venom repertoire.(AU)

Pedigree study of hereditary small cerebral vascular disease caused by c.821G＞A heterozygous mutation of HtrA serine protease-1 gene / 中华神经科杂志

Objective To investigate the clinical manifestations,imaging features,molecular genetic characteristics and possible pathogenic mechanisms of hereditary cerebral small vessel disease (CSVD) caused by heterozygous mutation of HtrA serine protease-1 (HTRA1) gene.Methods The clinical data of a Chinese Han family with CSVD carrying a heterozygous mutation of HTRA 1 gene,which came from the Department of Neurology,Henan Provincial People's Hospital in March 2018,were analyzed retrospectively.The clinical and radiographic features were summarized.Several high-throughput whole exon high-throughput sequencing was used to capture the mutation sites and the Sanger sequencing was used to validate the results.The family diagram was drawn and the 3D model construction and mutation function prediction were performed using silico tools.The relevant literature was reviewed and the pathogenesis was explored.Results The pedigree map showed that the family had an autosomal dominant inheritance pattern.Three generations of the family were investigated,and three family members in the same generation suffered from the disease.The first symptom of the proband was diplopia at the age of 39,accompanied by recurrent stroke,cognitive impairment and mood disorders,without alopecia.Head magnetic resonance imaging revealed bilateral diffuse,symmetric lesions,multiple lacunar infarcts,perivascular space,and microbleeds.The elder sister of the proband developed symptoms of left limb weakness at the age of 46,whose other clinical and imaging features were similar to those of the proband.The proband's mother died at the age of 59 due to repeated strokes.Whole exon sequencing indicated heterozygous missense mutation at c.821G＞A locus of HTRA1 gene in the proband and her 4th elder sibling,which was a new pathogenic mutation after consulting several mutation sites of databases.Function prediction suggested pathogenicity.Conclusions The heterozygous mutation of c.821G＞A in HTRA1 gene may lead to autosomal dominant CVSD.This genetic type should be given clinical attention.

Functional and biological insights of rCollinein-1, a recombinant serine protease from Crotalus durissus collilineatus

The prevalent class of snake venom serine proteases (SVSP) in Viperidae venoms is the thrombin-like enzymes, which, similarly to human thrombin, convert fibrinogen into insoluble fibrin monomers. However, thrombin-like serine proteases differ from thrombin by being unable to activate factor XIII, thus leading to the formation of loose clots and fibrinogen consumption. We report the functional and biological characterization of a recombinant thrombin-like serine protease from Crotalus durissus collilineatus, named rCollinein-1. Methods: Heterologous expression of rCollinein-1 was performed in Pichia pastoris system according to a previously standardized protocol, with some modifications. rCollinein-1 was purified from the culture medium by a combination of three chromatographic steps. The recombinant toxin was tested in vitro for its thrombolytic activity and in mice for its edematogenicity, blood incoagulability and effect on plasma proteins. Results: When tested for the ability to induce mouse paw edema, rCollinein-1 demonstrated low edematogenic effect, indicating little involvement of this enzyme in the inflammatory processes resulting from ophidian accidents. The rCollinein-1 did not degrade blood clots in vitro, which suggests that this toxin lacks fibrinolytic activity and is not able to directly or indirectly activate the fibrinolytic system. The minimal dose of rCollinein-1 that turns the blood incoagulable in experimental mice is 7.5 mg/kg. The toxin also led to a significant increase in activated partial thromboplastin time at the dose of 1 mg/kg in the animals. Other parameters such as plasma fibrinogen concentration and prothrombin time were not significantly affected by treatment with rCollinein-1 at this dose. The toxin was also able to alter plasma proteins in mouse after 3 h of injection at a dose of 1 mg/kg, leading to a decrease in the intensity of beta zone and an increase in gamma zone in agarose gel electrophoresis Conclusion: These results suggest that the recombinant enzyme has no potential as a thrombolytic agent but can be applied in the prevention of thrombus formation in some pathological processes and as molecular tools in studies related to hemostasis.(AU)

ANCA-positive vasculitis: Clinical implications of ANCA types and titers / Vasculite ANCA positiva: implicações clínicas dos tipos e dos títulos de ANCA

SUMMARY Introduction: Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis is an autoimmune disease that can affect multiple organs, the kidney being one of the most affected. Apart from the diagnostics value of ANCA, they have also been advocated as biomarkers of the disease activity. Recently, the genetic changes found in polyangiitis associated with serine-protease proteinase 3 (PR3)-ANCA or myeloperoxidase (MPO)-ANCA raised the possibility of immune-pathogenic and therapeutic differences. Objective: To identify differences in the number of relapses, inflammatory markers, outcomes and renal histology related to the types of ANCA. To analyze the implications of ANCA titers in prognosis. Method: A retrospective observational study in a Portuguese tertiary hospital. Results: There were no differences in the progression of renal function, histological pattern and initial treatment with regard to ANCA subtypes. As for the evaluated parameters, there were no significant differences according to the types of ANCA, except for mean CRP values within the normal range, which was 6.3±1.3 mg/L for MPO-ANCA and 12.4±10.14 mg/L for PR3-ANCA (p=0.04). We found that 66.7% of the MPO-ANCA-positive showed no relapses versus 40% in the case of PR3-ANCA-positive. There was no correlation between the ANCA titers at presentation, during remission, and in the last evaluation, and the number of relapses. Conclusion: PR3-ANCA patients have a mean CRP value within the normal range significantly higher than that of MPO-ANCA patients (p=0.04), which seems to reveal greater inflammatory activity in the first.

RESUMO Introdução: a vasculite associada aos anticorpos anticitoplasma de neutrófilos (ANCA) é uma doença autoimune que pode acometer vários órgãos, sendo o rim um dos mais afetados. Além dos ANCA serem marcadores de diagnóstico, foram também defendidos como marcadores de atividade. Recentemente as alterações genéticas encontradas entre as poliangeítes serina-protease 3 da proteinase (PR3)-ANCA ou mieloperoxidase (MPO)-ANCA levantam a possibilidade de diferenças imunopatogênicas e terapêuticas. Objetivos: identificar diferenças quanto a número de recidivas, marcadores inflamatórios, desfechos e histologia renal relativamente aos tipos de ANCA. Analisar implicações dos títulos de ANCA no prognóstico. Método: estudo retrospectivo observacional em hospital terciário português. Resultados: não se verificaram diferenças quanto à evolução da função renal, ao padrão histológico e ao tratamento inicial relativamente aos subtipos de ANCA. Nos parâmetros analíticos avaliados, não se verificaram diferenças significativas relativas aos tipos de ANCA, à exceção do valor médio de PCR no intervalo que foi de 6,3±1,3 mg/L nos MPO-ANCA e 12,4±10,14 mg/L nos PR3-ANCA (p=0,04). Verificamos que 66,7% dos MPO-ANCA positivos não apresentaram recidivas versus 40% dos PR3-ANCA positivos. Não se verificou nenhuma correlação entre os títulos de ANCA à apresentação, durante a remissão e na última avaliação com o número de recidivas. Conclusão: os indivíduos PR3-ANCA apresentaram um valor médio de PCR nos intervalos superior aos indivíduos MPO-ANCA (p=0,04), o que parece evidenciar uma maior atividade inflamatória nos primeiros.

Influence of down-regulation of HtrA1 expression by small interfering RNA on light-injured human retinal pigment epithelium cells / 中华眼底病杂志

Objective To observe the influence of down-regulation of HtrA1 expression by small interfering RNA on light-injured human retinal pigment epithelium (RPE) cells.Methods Cultured human RPE cells(8th-12th generations)were exposed to the blue light at the intensity of (2000 ± 500) Lux for 6 hours to establish the light injured model.Light injured cells were divided into HtrA1 siRNA group,negative control group and blank control group.HtrA1 siRNA group and negative control group were transfected with HtrA1 siRNA and control siRNA respectively.The proliferation of cells was assayed by CCK-8 method.Transwell test was used to detect the invasion ability of these three groups.Flow cytometry was used to detect the cell cycle and apoptosis.The expression of HtrA1 and vascular endothelial growth factor (VEGF)-A was detected by real time-polymerase chain reaction and Western blot respectively.Results The mRNA and protein level of HtrA1 in the light injured cells increased significantly compared to that in normal RPE cells (t=17.62,15.09;P＜0.05).Compared with negative control group and blank control group,the knockdown of HtrA1 in HtrA1 siRNA group was associated with reduced cellular proliferation (t=6.37,4.52),migration (t =9.56,12.13),apoptosis (t =23.37,29.08) and decreased mRNA (t=17.36,11.32,7.29,4.05) and protein levels (t=12.02,15.28,4.98,6.24) of HtrA1 and VEGF-A.Cells of HtrA1 siRNA group mainly remained in G0/G1 phase,the difference was statistically significant (t=6.24,4.93;P ＜0.05).Conclusion Knockdown of HtrA1 gene may reduce the proliferation,migration capability and apoptosis of light-injured RPE cells,and decrease the expression of VEGF-A.

Vasculite sistêmica da síndrome de Cogan associada ao PR3-ANCA. Relato de caso / Systemic vasculitis of Cogan's syndrome associated with PR3-ANCA. Case report

JUSTIFICATIVA E OBJETIVOS: A síndrome de Cogan (SC)caracteriza-se pela presença de ceratite intersticial não luética associada a manifestações de disfunção vestibulococlear. Este artigo tem como finalidade dar continuidade ao relato de caso da SC publicado nesse periódico em 2009, que mostra, agora em 2014, o acompanhamento ambulatorial durante 60 meses, os resultados laboratoriais, o tratamento realizado e faz uma breve revisão bibliográfica dos marcadores imunológicos. Também, como objetivo principal, apresentar essa rara entidade nosológica que, quando não tratada no início dos sintomas com imunossupressores, pode causar anacusia em 50% e amaurose em 10% dos pacientes e, em sua forma atípica, cursar com vasculite sistêmica. Como não encontramos citações na literatura mundial dessa associação - vasculite da SC com positividade de anticorpos dirigidos contra citoplasma de neutrófilos (c-ANCA) direcionados especificamente contra o antígeno serinaproteinase 3(PR3) - consideramos prudente novos artigos serem publicados no sentido de confirmar ou não esses achados clínico-laboratoriais. Ressaltamos que o paciente evoluiu satisfatoriamente para a cura, visto que permanece assintomático e com os exames de atividade inflamatória normais. RELATO DO CASO: Paciente do sexo masculino, 43 anos, branco, casado, comerciário,foi internado por 15 dias por apresentar hiperemia conjuntival, mialgias e febre com 30 dias de evolução. O diagnóstico foi realizado a partir do 11° dia, quando surgiram as seguintes manifestações: nistagmo, ataxia de marcha, tontura, náuseas e vômitos aos movimentos, dores articulares no punho, joelho e tornozelo esquerdos, acompanhadas de rubor e calor, acrescidas de sufusões hemorrágicas subungueais dolorosas em três dedos da mão esquerda, sugestivas de vasculite sistêmica. CONCLUSÃO: Este relato de caso apresenta aos profissionais médicos essa entidade rara, de difícil diagnóstico e de repercussões graves quando não bem tratada. Além disso,...

BACKGROUND AND OBJECTIVES: Cogan's syndrome (CS) is characterized by the occurrence of non-luetic intersticial keratitis associated with vestibulocochlear dysfunction signs. This article aims to give continuity to a report on the CS published in this journal in 2009, and proposes to show a 60-month outpatient follow-up, laboratory results and treatment prescribed, as well as to give a brief literature review on immunological markers, as far as 2014. It also has the primary aim of presenting this rare nosological entity which, if not treated with immunosuppressive drugs at the onset of symptoms, can lead to deafness in 50% of the patients and amaurosis in 10% of them, and occur concomitantly with systemic vasculitis in its atypical form. As international literature citations on the CS vasculitis association with positivity of antibodies against neutrophil cytoplasm (c-ANCA) specifically directed against cytoplasmic antigen serine proteinase 3 (PR3) have not been found, it is suggested that new articles should be published in order to either confirm or deny these clinical and laboratory findings. It is noteworthy that the patient progressed satisfactorily towards healing, and remains asymptomatic with negative inflammatory activity exam results. CASE REPORT: a 43 year-old married male Caucasian salesclerk from Piratini (RS) was hospitalized for a 15-day period showing conjunctival hyperemia, myalgia and fever following a thirty-day evolution period. Diagnosis was only reached on the 11th day when the following signs appeared: nystagmus, motor ataxia, dizziness, nausea and vomiting upon moving, joint pain in the left wrist, knee and ankle, accompanied by redness and heat, in addition to painful subungual hemorrhagic suffusions in three left-hand fingers compatible with systemic vasculitis. CONCLUSION: This case describes a rare syndrome of difficult diagnosis and serious implications when not properly treated...

Effects of matriptase down regulation on invasion of human pancreatic cancer cells SW1990 / 中华胰腺病杂志

Objective To investigate the effect of the down regulation of matriptase expression on invasion of human pancreatic cancers cells SW1990.Methods Small interfering RNA targeting at matriptase (Ma-siRNA) was transfected into human pancreatic cancers SW1990 cells,and nonsense siRNA (NC-siRNA) group was used as control.Real time PCR assay and Western blot were used to detect the expression of matriptase mRNA and protein.Transwell assay was used to examine the invasion ability of cancer cells.The enzymatic activity of matriptase and MMP-9 was determined by gelatin zymography assay.Results The expression level of matriptase mRNA in NC-siRNA group,12.5,25,50 nmol/L Ma-siRNA group were 1.000,0.417 ± 0.006,0.233 ± 0.068,0.221 ± 0.092;and the protein expression of matriptase were 0.736 ± 0.066,0.498 ± 0.036,0.341 ± 0.118,0.239 ± 0.050,respectively.The matriptase mRNA and protein expression in Ma-siRNA groups was significantly lower than those in NC-siRNA group,and the difference between the two groups was statistically significant (P ＜ 0.05).The enzymatic activity of matriptase were 1.501 ±0.165,1.211 ±0.265,0.645 ±0.165,0.620 ±0.003,and the enzymatic activity of MMP-9 were 0.929 ± 0.260,0.484 ± 0.364,0.352 ± 0.113,0.346 ± 0.121,and the enzymatic activity of matriptase and MMP-9 in 25,50 nmol/L Ma-siRNA groups was significantly lower than that in NC-siRNA group,and the difference was statistically significant (P ＜ 0.05 or ＜ 0.01).The number of transmembrane cell was (256 ± 1)/per 200 power field,and it was (109 ± 3)/per 200 power field in 25 nmol/L Ma-siRNA group,and the invasion ability of the cells in 25 nmol/L Ma-siRNA group was decreased by (57.4 ± 5.4) ％ when compared with that of control group.Conclusions Down-regulation of matriptase inhibits invasion ability of pancreatic cancer SW1990 cells,and this result may be due to the down regulated enzymatic activity of matriptase and MMP-9.

Changes in the Expression and Distribution of Claudins, Increased Epithelial Apoptosis, and a Mannan-Binding Lectin-Associated Immune Response Lead to Barrier Dysfunction in Dextran Sodium Sulfate-Induced Rat Colitis

BACKGROUND/AIMS: This animal study aimed to define the underlying cellular mechanisms of intestinal barrier dysfunction. METHODS: Rats were fed 4% with dextran sodium sulfate (DSS) to induce experimental colitis. We analyzed the sugars in 24-hour urine output by high pressure liquid chromatography. The expression of claudins, mannan-binding lectin (MBL), and MBL-associated serine proteases 2 (MASP-2) were detected in the colonic mucosa by immunohistochemistry; and apoptotic cells in the colonic epithelium were detected by the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling method assay. RESULTS: The lactulose and sucralose excretion levels in the urine of rats with DSS-induced colitis were significantly higher than those in the control rats. Mannitol excretion was lower and lactulose/mannitol ratios and sucralose/mannitol ratios were significantly increased compared with those in the control group (p<0.05). Compared with the controls, the expression of sealing claudins (claudin 3, claudin 5, and claudin 8) was significantly decreased, but that of claudin 1 was increased. The expression of pore-forming claudin 2 was upregulated and claudin 7 was downregulated in DSS-induced colitis. The epithelial apoptotic ratio was 2.8%+/-1.2% in controls and was significantly increased to 7.2%+/-1.2% in DSS-induced colitis. The expression of MBL and MASP-2 in the intestinal mucosa showed intense staining in controls, whereas there was weak staining in the rats with colitis. CONCLUSIONS: There was increased intestinal permeability in DSS-induced colitis. Changes in the expression and distribution of claudins, increased epithelial apoptosis, and the MASP-2-induced immune response impaired the intestinal epithelium and contributed to high intestinal permeability.

Relationship between TMPRSS4 and tumor invasion and metastasis / 国际外科学杂志

Type Ⅱ transmembrane serine proteases 4 (TMPRSS4) is a novel type Ⅱ transmembrane serine protease.Present study showed that its expression was related with tumor invasion and metastasis,although its oncogenic significance and molecular mechanisms are still unknown.In this review,the author try to introduce its structure,biological function and mechanism in tumor invasion and metastasis.

The Comparison of Parathyroid Hormone Degradation Effect by Various Protease Inhibitors in Blood Specimen / 대한진단검사의학회지

BACKGROUND: The objective of this study was to evaluate the role of proteases on the degradation of parathyroid hormone (PTH) in blood samples. METHODS: Protease inhibitors with specificity against serine proteases (aprotinin), cysteine proteases (E-64), serine and cysteine proteases (leupeptin), metalloproteases (EDTA), or a protease inhibitor cocktail with a broad spectrum of inhibitory activity were added to blood samples. After storage at room temperature (0-48 hr), PTH levels were measured. RESULTS: PTH levels in samples with the protease inhibitor cocktail did not change significantly after 48 hr of storage at room temperature, but the average PTH levels decreased by 40.7% and 20.1%, in samples stored at room temperature and stored at 4degrees C without protease inhibitors, respectively. PTH levels in samples with leupeptin were stable for up to 24 hr. After 48 hr, the mean PTH levels decreased by 17.1%, 16.0%, 26.2%, and 32.1%, with 500 KIU/mL aprotinin, 100 micro mol/L leupeptin, 10 micro mol/L E-64, and 10 micro mol/L EDTA, respectively, in the samples stored at room temperature. CONCLUSIONS: The decrease in PTH levels in blood samples seemed to be due to the degradation of PTH by proteases. Various proteases, including especially serine proteases, would act together to degrade PTH in blood specimen. The PTH degradation may be inhibited in blood specimen with protease inhibitor cocktail.

Serine protease activities in Oxysarcodexia thornax (Walker) (Diptera: Sarcophagidae) first instar larva

We report for the first time the expression of multiple protease activities in the first instar larva (L1) of the flesh fly Oxysarcodexia thornax (Walker). Zymographic analysis of homogenates from freshly obtained L1 revealed a complex proteolytic profile ranging from 21.5 to 136 kDa. Although some activities were detected at pH 3.5 and 5.5, the optimum pH for most of the proteolytic activities was between pH 7.5 and 9.5. Seven of 10 proteases were completely inactivated by phenyl-methyl sulfonyl-fluoride, suggesting that main proteases expressed by L1 belong to serine proteases class. Complete inactivation of all enzymatic activities was obtained using N-p-Tosyl-L-phenylalanine chloromethyl ketone (100 µM), a specific inhibitor of chymotrypsin-like serine proteases.

A Member of Ⅱ Transmembrane Serine,TMPRSS3 and Hereditary Deafness / 生物化学与生物物理进展

TMPRSS3 (transmembrane protease, serine 3) is a member of Ⅱ transmembrane serine proteases (TTSPs), and like the other members of this family, it contains typical domains including a serine protease domain, a transmembrane domain, a LDL receptor-like domain (LDLRA), and a scavenger receptor cysteine-rich domain (SRCR). Four alternative protein isoforms have been described, and isoform A is thought to be primary isoform which is expressed in many tissues, especially in the cochlea. TMPRSS3 protein is primarily localized in the endoplasmic reticulum membranes where it may be anchored by its transmembrane domain. TMPRSS3 is mutated in non-syndromic autosomal recessive deafness (DFNB8/10). Therefore TMPRSS3 is thought to be involved in the development and maintenance of the inner ear, and isoform D may be proposed as a novel diagnostic marker in ovarian carcinoma. TMPRSS3 protein is the first protease which mutation could lead to deafness. These data indicate that important signaling pathways in the inner ear are controlled by proteolytic cleavage. However, it is not clear about TMPRSS3 substrates and its function. The epithelial amiloride-sensitive sodium channel (ENaC) which is regulated by membrane-bound channel activating serine proteases (CAPs), a member of TTSPs, may be a potential substrate of TMPRSS3, but this hypothesis is still to be verified in vivo. With the development of protease research and the application of protease proteomics, substrate degradomes of a protease may therefore represent an important tool for the research of TMPRSS3 function and its molecular mechanism.

Investigation on Clinical Effect of Ciwujia Injection and Jiangxianmei Combination for Acute Cerebral Infarction / 中成药

Objective:To investigate the effect of ciwujia Injection and Jiangxianmei combination for acute cerebral infarction. Methods:86 patients with cerebral infarction were divided into 2 groups. 43 cases in the treatment group were dripped intravenously with 60ml ciwujia Injection and 250ml physiological saline. 43 cases in the control group were treated only with Jiangxianmei. Both of groups were also treated with other therapeutic method. The hemorheology and blood fat of patients in two groups before and after treatment were determined. Results:The cure rate of the treatment groups in two weeks was 41.86%, which is superior to the control group (20.93%) ( x 2=4.37,P0.05). The treatment group was superior to the control group in improving hemorheological index and blood fat metabolism ( P

Quantum-Chemical Study of Catalytic Mechanism of Serine Proteases (III) / 昆明医科大学学报

In this paper, the model system of proton transfer with the water molecule as an intermediate acceptor of Ser-195 was suggested and analysed by the CNDO/2 method. The acylation activation barrier of this system was shown to restrict the stage of synchronous transfer of the Ser-195 alcoholic proton and the water molecule proton hydrogen bound to His-57 N~(?_2)-atom to the water molecule oxygen atom and the N~(?_2)-atom, respectively. The substrate protonation in the case of the model system with the water molecule as the in ermediate acceptor was demonstrated to begin before the completion of the tetrahedral inermediate substance, only the protonated form of the tetrahedal intermediate being shown. A lypothesis of considering the role of this water molecule as a nuclephilic reagent in the leacylation stage is presented.

A Quantum Chemical Study on The Catalytic Mechanism of Serine Proteases(Ⅰ) / 昆明医科大学学报

Using the semi-empirical MNDO/H method several systems simulating the reaction of tetrahetral intermediate formation in the active site of serine proteases have been studied. The role played by elements of the《catalytic triad》in increasing the reactivity of serine hydroxyl has been discussed.The formation of a strong hydrogen bond between His and Asp was shown to be important in lowering the activation energy in the reaction of Ser with substrate.The change in position of the proten located between Ser and His and between His and Asp was analysed.The influence of substrate distortion on the energy of intermediate formation has been considered.

Ouantum Chemical Study on Catalytic Mechanism of Serine Proteases / 昆明医科大学学报

Using the semiempirical MNDO method,several systems simulating the active site of serine proteases have been studied.The stabilization energy was found depending strongly on the nucleophilicity of the attacking group.the decrease of the activation energy has been esti- mated at 9 kca/mole.It was shown that the substrate distortion did not vary with the form- ing of hydrogen bonds.

Studies on plant gums. Proteases in neem (Azadirachta indica) gum.

Proteolytic activity was detected in neem (Azadirachta indica) exudate gum when tested with casein and albumin as substrates. The enzyme activity was separated into two fractions by chromatography on TEAE-cellulose after EDTA treatment. Both the enzyme fractions were fairly stable to high temperatures and wide range of pH conditions. The pH optima were found to be around 6·5. Phenylmethyl sulphonylfluoride inhibited the activity of both the fractions. EDTA, ß-mercaptoethanol, tosylamide phenylethylchloromethylketone, tosyllysine chloroimethylketone, p-chloromercuribenzoate and dithiobis-2-nitrobenzoie acid did not affect the activity of the two enzyme fractions. The two fractions had no hydrolytic action on a variety of synthetic substrates tested.