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2.
Eur Rev Med Pharmacol Sci ; 26(11): 4028-4043, 2022 06.
Artigo em Inglês | MEDLINE | ID: mdl-35731074

RESUMO

OBJECTIVE: Oxaliplatin-induced neuropathy is a significant complication of cancer therapy. We aimed at investigating the risk factors of oxaliplatin-induced neuropathy (OIPN) and providing evidence to enhance its prevention. MATERIALS AND METHODS: PubMed, Medline, Web of Science, Embase, China Knowledge Resource Integrated Database, and the Wanfang Database were searched comprehensively for observational studies investigating the prevalence and risk factors of OIPN from inception to November 30, 2021. The Newcastle-Ottawa Scale was used by two independent reviewers to assess methodological quality. When applicable, we used meta-analysis to determine mean differences and odds ratios for continuous and nominal scaled data. RESULTS: We included 20 studies involving 10,900 participants for analysis. Factors associated with OIPN risk identified by meta-analysis were age, gender, diabetes, anemia, hypomagnesaemia, alcohol consumption, body mass index, body surface area, cumulative oxaliplatin dose and the number of chemotherapy cycles. Factors not associated with OIPN risk included smoking history and chemotherapy regimen. CONCLUSIONS: This meta-analysis identified multiple variables associated with OIPN. The recognition of modifiable risk factors is an urgent priority to improve prevention and treatment outcomes.


Assuntos
Antineoplásicos , Doenças do Sistema Nervoso Periférico , Antineoplásicos/efeitos adversos , China , Humanos , Oxaliplatina/efeitos adversos , Doenças do Sistema Nervoso Periférico/induzido quimicamente , Doenças do Sistema Nervoso Periférico/tratamento farmacológico , Doenças do Sistema Nervoso Periférico/epidemiologia , Fatores de Risco , Resultado do Tratamento
3.
Zhonghua Xue Ye Xue Za Zhi ; 40(6): 490-496, 2019 Jun 14.
Artigo em Chinês | MEDLINE | ID: mdl-31340622

RESUMO

Objective: To investigate the proteins expression difference after upregulation of human CD99 in Hodgkin Lymphoma cell line, L428 cell, and verify the function of differential proteins. Methods: The differential proteins were detected by two-dimensional fluorescence difference gel electrophoresis and mass spectrometry analysis, cluster analysis was done by GOfact. Results: There were 38 proteins screened out, of which 21 proteins were positively associated with CD99, while 17 proteins were negative. Among the 38 proteins, 32 proteins participated in biological process, and 35 proteins were involved in the composition and construction. And 28 proteins participated in multifaceted biological activities including antioxidation, protein binding, catalytic activity, regulation of enzyme, signal transduction, molecular structure, regulation of translation and ion transport. Conclusions: The changes of the differential proteins, correlated with cytoskeleton, cell differentiation, signal pathway and regulating gene expression, are closely relevant to the translation between Hodgkin/Reed-Sternberg and B lymphocyte cell.


Assuntos
Doença de Hodgkin , Antígeno 12E7 , Linhagem Celular Tumoral , Humanos , Proteômica , Regulação para Cima
4.
Eur Rev Med Pharmacol Sci ; 23(5): 1891-1898, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30915731

RESUMO

OBJECTIVE: The aim of this study was to investigate the effects of miR-92b-5p inhibitor and interleukin-18-binding protein (IL-18BP) on interleukin-18 (IL-18)-mediated inflammatory response after spinal cord injury (SCI). MATERIALS AND METHODS: In this work, microglia was isolated from the newborn C57/B6J mice spinal cord to in vitro culture. The expression of IL-18BP and IL-18 was measured by the quantitative Real Time-Polymerase Chain Reaction (qRT-PCR) after transfection of miR-92b-5p into activated microglia. The expression of IL-18BP and IL-18 was determined following miR-92b-5p inhibitor treatment. In addition, the spinal cord injury model was established in mice. The expressions of miR-92b-5p, IL-18BP, and IL-18 were measured by qRT-PCR, and the expressions of inducible nitric oxide synthase (iNOS), tumor necrosis factor (TNF-α) and interleukin-1 ß (IL-1 ß) were determined by Western blot. After intrathecal injection of miR-92b-5p inhibitor, the mRNA expression of miR-92b-5p, IL-18BP, and IL-18 and the expression of iNOS, TNF-α, and IL-1 ß in the injured area of the spinal cord of mice were measured. Basso Mouse Scale (BMS) was used to determine the recovery of locomotor function after spinal cord injury and miR-92b-5p inhibition. RESULTS: After miR-92b-5p transfection, the expression of IL-18BP was significantly decreased compared with that of untransfected microglia cells, whereas the level of IL-18 mRNA was significantly increased. However, the level of IL-18BP elevated significantly and the level of IL-18 reduced markedly after treatment with corresponding inhibitors. In addition, compared with the sham operation group (Sham), the RNA level of miR-92b-5p in the SCI group was significantly higher than that in the Sham, but the expression of IL-18BP was evidently declined and the expression of IL-18 was significantly increased in the SCI group. Meanwhile, the expression of miR-92b-5p in miR-92b-5p inhibitor intrathecal injection mice was remarkably lower than that in SCI group, the expression level of IL-18BP was significantly increased, and the RNA expression of IL-18 was weakened accordingly. Moreover, the protein expression of iNOS, TNF-α, and IL-1 ß in miR-92b-5p inhibitor-treated mice was significantly lower than that in the SCI group. The locomotor evaluation of miR-92b-5p inhibitor group was dramatically higher than that of the SCI group. CONCLUSIONS: Suppressing the expression of miR-92b-5p after SCI can effectively intensify the level of IL-18BP, reduce the expanded inflammatory effect of IL-18, decline the release of iNOS, TNF-α, and IL-1 ß, thus alleviate the neuronal injury and improve the locomotor function after SCI.


Assuntos
Peptídeos e Proteínas de Sinalização Intercelular/metabolismo , Interleucina-18/metabolismo , MicroRNAs/genética , Microglia/imunologia , Traumatismos da Medula Espinal/imunologia , Medula Espinal/imunologia , Animais , Células Cultivadas , Modelos Animais de Doenças , Peptídeos e Proteínas de Sinalização Intercelular/genética , Interleucina-18/genética , Masculino , Camundongos Endogâmicos C57BL , MicroRNAs/antagonistas & inibidores , Microglia/metabolismo , Atividade Motora/genética , Cultura Primária de Células , Medula Espinal/metabolismo , Traumatismos da Medula Espinal/genética , Traumatismos da Medula Espinal/metabolismo , Transfecção
5.
Allergy ; 72(12): 1972-1987, 2017 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-28580587

RESUMO

BACKGROUND: Specific JAK/STAT pathways play a critical role in the functional differentiation of distinct Th subsets. Previously, we showed that HO-1, a stress-inducible protein, inhibits Th17 cell differentiation and alleviates neutrophilic airway inflammation, but the responsible molecular basis remains unclear. METHODS: We employed Th17-skewing differentiation and NEA mouse models to study the role of HO-1 in regulating IL-6-STAT3-RORγt/SOCS3 signaling pathway to control Th17 cell-mediated neutrophilic airway inflammation. The levels of cytokines and expressions of relative signaling molecules were measured by ELISA, western blot, and qPCR, respectively. Frequency of CD4+ IL-17A+ , CD4+ IL-6R+ , and CD4+ IL-23R+ cells was analyzed by FCM. The interaction between HO-1 and signaling pathway-related proteins was determined by co-immunoprecipitation and western blot. RESULTS: Here, we show that hemin-induced HO-1 overexpression is required to mediate this process. Specifically, HO-1 decreased STAT3 phosphorylation but not IL-6R/IL-23R expression or JAK1/JAK2 activation in CD4+ T cells. The effect was accompanied by co-inhibition of SOCS3, a negative feedback factor of STAT3 activation. HO-1 bound to three domains on STAT3 (DNA-binding, linker, and transactivation domains) to directly regulate STAT3 activation. Conversely, either forced expression of a constitutively active STAT3 mutant or application of small-interfering RNA (siRNA) for HO-1 reversed these effects. CONCLUSIONS: Our data suggest that HO-1 exerts its inhibitory effect on Th17 cell differentiation by directly associating and blocking STAT3 phosphorylation. We speculate that hemin may be a potential therapeutic candidate for the treatment of other types of immune and pulmonary inflammatory-related diseases.


Assuntos
Heme Oxigenase-1/metabolismo , Inflamação/etiologia , Inflamação/metabolismo , Neutrófilos/imunologia , Neutrófilos/metabolismo , Fator de Transcrição STAT3/metabolismo , Células Th17/imunologia , Células Th17/metabolismo , Animais , Linhagem Celular , Modelos Animais de Doenças , Feminino , Expressão Gênica , Heme Oxigenase-1/genética , Humanos , Imunidade , Inflamação/patologia , Interleucina-6/metabolismo , Janus Quinases/metabolismo , Camundongos , Infiltração de Neutrófilos , Neutrófilos/patologia , Membro 3 do Grupo F da Subfamília 1 de Receptores Nucleares/metabolismo , Fosforilação , Plasmídeos/genética , Ligação Proteica , RNA Interferente Pequeno/genética , Doenças Respiratórias/etiologia , Doenças Respiratórias/metabolismo , Doenças Respiratórias/patologia , Fator de Transcrição STAT3/genética , Transdução de Sinais , Transfecção
6.
Genet Mol Res ; 15(4)2016 Oct 05.
Artigo em Inglês | MEDLINE | ID: mdl-27808358

RESUMO

Laryngeal cancer is the major malignant tumor affecting the upper respiratory tract. Previous studies have reported on the association between XRCC1 genetic polymorphisms and risk of laryngeal cancer, but with conflicting results. In this study, we attempted to assess the association between XRCC1 Arg194Trp, Arg280His and Arg399Gln polymorphisms and risk of laryngeal cancer in a Chinese population. A total of 126 laryngeal cancer patients and 254 control subjects were recruited to this study from the Second Medical College of Jinan University between December 2013 and May 2015. The XRCC1 Arg194Trp, Arg280His, and Arg399Gln polymorphic sites were genotyped by polymerase chain reaction-restriction fragment length polymorphism. Our results revealed a significant association between the AA genotype of XRCC1 Arg280His [odds ratio (OR) = 2.51, 95% confidence interval (CI) = 1.29-4.87, P = 0.01] and an increased risk of laryngeal cancer susceptibility compared to the GG genotype. Moreover, the A allele showed a higher risk of laryngeal cancer susceptibility compared to the G allele (OR = 1.63, 95%CI = 1.19-2.50, P = 0.002). In conclusion, the results of our study suggest that the AA genotype and A allele of the XRCC1 Arg280His polymorphism are associated with an increased laryngeal cancer risk in a Chinese population.


Assuntos
Povo Asiático/genética , Proteínas de Ligação a DNA/genética , Estudos de Associação Genética , Predisposição Genética para Doença , Neoplasias Laríngeas/genética , Polimorfismo de Nucleotídeo Único/genética , Demografia , Feminino , Humanos , Estilo de Vida , Masculino , Pessoa de Meia-Idade , Proteína 1 Complementadora Cruzada de Reparo de Raio-X
7.
Eur Rev Med Pharmacol Sci ; 20(10): 2077-89, 2016 05.
Artigo em Inglês | MEDLINE | ID: mdl-27249608

RESUMO

OBJECTIVE: Acute Fibrinous and Organizing Pneumonia (AFOP) is a new pathologic pattern of acute lung injury characterized by the presence of intra-alveolar fibrin in the form of fibrin "balls" in a patchy distribution. CASE REPORT: A 65-years-old female after a surgical resection of rectal adenocarcinoma presented with typical manifestations of hospital-acquired pneumonia, but she didn't respond to the anti infective therapy. After an explicit diagnosis of AFOP via percutaneous needle lung biopsy, she got an impressive improvement with a long-term therapy of methylprednisolone and low-dose indomethacin. To date, a total of non-overlapped 45 individual AFOP cases and 4 single-center studies involving AFOP have been reported. The most common coexisting diseases are infections, connective tissue diseases and hematological diseases. Corticosteroids and immunosuppressants are the most common agents prescribed in AFOP. The prognosis of AFOP is unfavorable, associated with the pathologic characteristics and the clinical parameters. CONCLUSIONS: The immune system activated by infection may play an important role in the pathogenesis of AFOP. Low-dose indomethacin combined with methylprednisolone may be a new choice for AFOP treatment.


Assuntos
Adenocarcinoma/complicações , Adenocarcinoma/cirurgia , Pneumonia , Neoplasias Retais/complicações , Neoplasias Retais/cirurgia , Adenocarcinoma/diagnóstico , Anti-Inflamatórios/uso terapêutico , Infecção Hospitalar , Feminino , Humanos , Indometacina/uso terapêutico , Metilprednisolona/uso terapêutico , Pneumonia/diagnóstico , Pneumonia/tratamento farmacológico , Pneumonia/etiologia , Neoplasias Retais/diagnóstico
8.
Beijing Da Xue Xue Bao Yi Xue Ban ; 48(2): 304-9, 2016 Apr 18.
Artigo em Chinês | MEDLINE | ID: mdl-27080286

RESUMO

OBJECTIVE: To detect the proportion of lymphocyte subsets in peripheral blood of the advanced breast cancer patients before and after chemotherapy with docetaxel and thiotepa, as well as the association between the proportion of peripheral blood lymphocyte subsets with the response rate and prognosis. METHODS: The proportions of lymphocyte subsets (CD3+ T cell, CD3+/CD4+ T cell, CD3+/CD8+ T cell, CD3-/CD16+56+ NK cell, CD3+/CD16+56+ T cell, CD19+ B cell, CD4+/CD25+ T cell, CD8+/CD28- T cell, CD8+/CD28+ T cell) in the peripheral blood of 86 patients were analyzed with flowcytometry before and after chemotherapy. The result was analyzed in combination with clinicopathological data. RESULTS: The proportion of regulatory T cells (Treg) after chemotherapy in the disease control patients decreased significantly compared with that of the progressive patients (P=0.034). The difference of the proportions of Treg before and after chemotherapy affected significantly the overall survival (OS). The OS of the patients with decreased proportion of Treg was significantly longer than that of the patients with increased proportion of Treg, which was 23.5 and 9.4 months respectively (P<0.05). CONCLUSION: The patients with decreased proportion of Treg after chemotherapy had higher response rate and better survival benefit.


Assuntos
Neoplasias da Mama/sangue , Subpopulações de Linfócitos T/citologia , Linfócitos T Reguladores/citologia , Neoplasias da Mama/tratamento farmacológico , Neoplasias da Mama/imunologia , Docetaxel , Feminino , Citometria de Fluxo , Humanos , Contagem de Linfócitos , Metástase Neoplásica/tratamento farmacológico , Metástase Neoplásica/imunologia , Prognóstico , Taxa de Sobrevida , Taxoides/uso terapêutico
9.
Eur Rev Med Pharmacol Sci ; 19(14): 2634-40, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26221894

RESUMO

A 44-year-old man presented with chronic, persistent cough and occasional wheezing. Airflow obstruction, blood eosinophilia and a remarkable elevated level of serum carcinoembryonic antigen (CEA) were found. Radiographic and pathological studies confirmed eosinophilic bronchiolitis. There was no evidence of neoplasms by extensive examinations. After a protracted oral steroid therapy, the blood eosinophil count, the serum CEA level and the lung lesions were all improved in parallel, whereas fixed airflow obstruction remained. This case was diagnosed as a new distinct syndrome, hypereosinophilic obliterative bronchiolits. Serum CEA and blood eosinophil cell count served as good markers of the disease condition for this syndrome.


Assuntos
Bronquiolite Obliterante/sangue , Bronquiolite Obliterante/diagnóstico , Antígeno Carcinoembrionário/sangue , Síndrome Hipereosinofílica/sangue , Síndrome Hipereosinofílica/diagnóstico , Adulto , Biomarcadores/sangue , Bronquiolite Obliterante/complicações , Tosse/sangue , Tosse/diagnóstico , Tosse/etiologia , Humanos , Síndrome Hipereosinofílica/complicações , Masculino
10.
Br J Cancer ; 110(3): 808-16, 2014 Feb 04.
Artigo em Inglês | MEDLINE | ID: mdl-24169354

RESUMO

BACKGROUND: Intakes of choline and betaine have been inversely related to the risk of various neoplasms, but scant data exist on nasopharyngeal carcinoma (NPC). We examined the association between consumption of choline and betaine and risk of NPC. METHODS: We conducted a case-control study with 600 incident NPC patients and 600 controls 1 : 1 matched by age, sex and household type in Guangdong, China. Dietary intake was assessed by a food frequency questionnaire through face-to-face interview. RESULTS: Intakes of total choline, betaine and choline+betaine were inversely related to NPC after adjustment for various lifestyle and dietary factors (all P-trend <0.001). Adjusted odds ratios (95% CI) for quartile 4 (vs quartile 1) were 0.42 (0.29, 0.61) for total choline, 0.50 (0.35, 0.72) for betaine and 0.44 (0.30, 0.64) for betaine+total choline. Regarding various sources of choline, lower NPC risk was associated with greater intakes of choline from phosphatidylcholine, free choline, glycerophosphocholine and phosphocholine, but not sphingomyelin. CONCLUSION: These findings are consistent with a beneficial effect of choline and betaine intakes on carcinogenesis.


Assuntos
Betaína/administração & dosagem , Colina/administração & dosagem , Neoplasias Nasofaríngeas/dietoterapia , Neoplasias Nasofaríngeas/patologia , Adulto , Idoso , Carcinogênese/efeitos dos fármacos , Carcinoma , Estudos de Casos e Controles , China , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Carcinoma Nasofaríngeo , Neoplasias Nasofaríngeas/epidemiologia , Fatores de Risco , Inquéritos e Questionários
11.
Oncogene ; 26(10): 1385-97, 2007 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-16953224

RESUMO

Constitutively activated nuclear factor-kappaB (NF-kappaB) has been associated with a variety of aggressive tumor types, including head and neck squamous cell carcinoma (HNSCC); however, the mechanism of its activation is not fully understood. Therefore, we investigated the molecular pathway that mediates constitutive activation of NF-kappaB in a series of HNSCC cell lines. We confirmed that NF-kappaB was constitutively active in all HNSCC cell lines (FaDu, LICR-LON-HN5 and SCC4) examined as indicated by DNA binding, immunocytochemical localization of p65, by NF-kappaB-dependent reporter gene expression and its inhibition by dominant-negative (DN)-inhibitory subunit of NF-kappaB (IkappaBalpha), the natural inhibitor of NF-kappaB. Constitutive NF-kappaB activation in HNSCC was found to be due to constitutive activation of IkappaBalpha kinase (IKK); and this correlated with constitutive expression of phosphorylated forms of IkappaBalpha and p65 proteins. All HNSCC showed the expression of p50, p52, p100 and receptor-interacting protein; all linked with NF-kappaB activation. The expression of constitutively active NF-kappaB in HNSCC is mediated through the tumor necrosis factor (TNF) signaling pathway, as NF-kappaB reporter activity was inhibited by DN-TNF receptor-associated death domain (TRADD), DN-TNF receptor-associated factor (TRAF)2, DN-receptor-interacting protein (RIP), DN-transforming growth factor-beta-activated kinase 1 (TAK1), DN-kappa-Ras, DN-AKT and DN-IKK but not by DN-TRAF5 or DN-TRAF6. Constitutive NF-kappaB activation was also associated with the autocrine expression of TNF, TNF receptors and receptor-activator of NF-kappaB and its ligand in HNSCC cells but not interleukin (IL)-1beta. All HNSCC cell lines expressed IL-6, a NF-kappaB-regulated gene product. Furthermore, treatment of HNSCC cells with anti-TNF antibody downregulated constitutively active NF-kappaB, and this was associated with inhibition of IL-6 expression and cell proliferation. Our results clearly demonstrate that constitutive activation of NF-kappaB is mediated through the TRADD-TRAF2-RIP-TAK1-IKK pathway, making TNF a novel target in the treatment of head and neck cancer.


Assuntos
Carcinoma de Células Escamosas/metabolismo , Neoplasias de Cabeça e Pescoço/metabolismo , NF-kappa B/biossíntese , Linhagem Celular Tumoral , Proliferação de Células , Humanos , Quinase I-kappa B/metabolismo , Proteína Serina-Treonina Quinases de Interação com Receptores/metabolismo , Receptores Tipo I de Fatores de Necrose Tumoral/metabolismo , Transdução de Sinais , Proteína de Domínio de Morte Associada a Receptor de TNF/metabolismo , Fator 2 Associado a Receptor de TNF/metabolismo , Fator de Transcrição RelA , Fatores de Crescimento Transformadores/metabolismo
12.
World J Gastroenterol ; 7(4): 559-62, 2001 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-11819829

RESUMO

AIM: To clone the cDNA fragment of human TRAIL (TNF-related apoptosis inducing ligand) into a tetracycline-regulated gene expression system, the RevTet-On system, transduce expression vectors into a gastric carcinoma cell line-NCI-N87 and examine the effects of controlled expression of TRAIL in vitro on the gastric carcinoma cells. METHODS: The full-length cDNA of TRAIL was inserted into a vector under the control of the tetracycline-responsive element (TRE) to obtain the plasmid pRevTRE-TRAIL, which was transfected into a packaging cell line PT67. In addition, vector pRev-Tet On and pRevTRE were also transfected into PT67 separately. After hygromycin and G418 selection, the viral titer was determined. The medium containing retroviral vectors was collected and used to transduce a gastric carcinoma cell line NCI-N87. The resulting cell line NCI-N87-Tet On TRE-TRAIL and a control cell line, NCI-N87 Tet On-TRE, were established. TRAIL expression in the cell line was induced by incubating cells with doxycycline (Dox), which is a tetracycline analogue. The killing effect on gastric carcinoma cells was analyzed after induction. RESULTS: The recombinant plasmid pRev-TRE-TRAIL was constructed. After hygromycin or G418 selection, the producer cell lines PT67-TRE, PT67-TRE-TRAIL and PT67-Tet On were obtained,with titers of about 10(8)CFU.L(-1). By transducing NCI-N87 cells with retroviral vectors from these cell lines, stable cell lines NCI-N87-Tet-On TRE-TRAIL (NN3T) and control cell line NCI-N87-Tet-On-TRE (NN2T) were established. The growth curves of the selected cell lines were the same with the wild type NCI-N87. When Dox was added, cell death was obvious in the test groups (29%-77%), whereas no difference was observed in control and wild type cell lines. With the addition of a medium from the test group, human leukemia cell line Jurkat was activated till death (83%), indicating the secretion of active TRAIL proteins from the test cells to the medium. CONCLUSION: With the use of the RevTet-On system, a regulated expression system for TRAIL was constructed. Using this system, the selected killing effect of TRAIL on gastric carcinoma cell line NCI-N87 could be observed.


Assuntos
Antibacterianos/farmacologia , Apoptose/fisiologia , Doxiciclina/farmacologia , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Glicoproteínas de Membrana/genética , Neoplasias Gástricas , Fator de Necrose Tumoral alfa/genética , Células 3T3 , Animais , Proteínas Reguladoras de Apoptose , Vetores Genéticos , Humanos , Células Jurkat , Camundongos , Retroviridae/genética , Ligante Indutor de Apoptose Relacionado a TNF , Transfecção
13.
Sheng Li Ke Xue Jin Zhan ; 32(1): 18-22, 2001 Jan.
Artigo em Chinês | MEDLINE | ID: mdl-12545771

RESUMO

TRAIL (TNF-related apoptosis inducing ligand) belongs to the tumor necrosis factor (TNF) cytokine family, can induce apoptosis in a wide variety of tumor cell lines. This review introduces research progress on TRAIL from several aspects: the structure and function of TRAIL, the pathway of its inducing apoptosis, TRAIL and cancer treatment, and its foreground.


Assuntos
Glicoproteínas de Membrana/fisiologia , Neoplasias/terapia , Fator de Necrose Tumoral alfa/fisiologia , Animais , Antineoplásicos , Proteínas Reguladoras de Apoptose , Proteína Ligante Fas , Humanos , Ligante Indutor de Apoptose Relacionado a TNF , Receptor fas
14.
J Biol Chem ; 265(3): 1496-501, 1990 Jan 25.
Artigo em Inglês | MEDLINE | ID: mdl-2104844

RESUMO

The specificity of thermopsin, a thermostable acid protease from Sulfolobus acidocaldarius, was studied using oxidized insulin B chain as substrate followed by peptide isolation and identification. The following bonds were hydrolyzed: Leu-Val, Leu-Tyr, Phe-Phe, Phe-Tyr, and Tyr-Thr. Thus, the specificity of thermopsin is similar to that of pepsin, that is, it prefers large hydrophobic residues at both sides of the scissile bond. We confirmed this by the use of a synthetic substrate, Lys-Pro-Ala-Glu-Phe-p-nitro-phenylalanyl-Ala-Leu, which was cleaved by thermopsin between Phe and p-nitro-phenylalanyl. Using this substrate, enzyme inhibition and kinetic properties of thermopsin have been studied. Thermopsin optimally hydrolyzes this substrate at 75 degrees C and pH 2 with Km and kcat values under these conditions of 5.3 x 10(-5) M and 14.3 s-1, respectively. Pepstatin competitively inhibits thermopsin with a Ki of 2 x 10(-7) M. Other known aspartic protease inhibitors, diazoacetylnorleucine ethyl ester and 1,2-epoxy-3-(p-nitrophenoxy)propane inhibited thermopsin only slowly and with nonspecific reactions. Although thermopsin contains a single cysteine, iodoacetic acid and p-chloromercuric benzoate had no effect on activity. Mercuric chloride inhibited the enzyme, and the inhibition was reversible by mercaptoethanol. However, the enzyme was not labeled by [14C]iodoacetic acid either before or after sodium dodecyl sulfate denaturation. Thus, the thiol group is likely blocked, and the inhibition effect of mercuric ion is unrelated to the thiol group. These observations suggest that thermopsin has a different active site than the aspartic protease family but may have a similar transition state structure. The temperature dependence of Km and kcat was studied for thermopsin hydrolysis of the synthetic substrate between 26-78 degrees C. Both parameters increased with temperature, and the rise of kcat value was particularly sharp above 65 degrees C. Hydrolysis activity measured at high substrate concentration has a maximum at 76 degrees C, which is near the physiological temperature for the optimal growth of this organism. Thus, thermopsin appears to function best at high temperature and high substrate concentration. It may be utilized by the organism to response to the presence of high substrate concentration in the medium. Thermopsin is also competitively inhibited by urea, acetamide, and phenylalaninamide with Ki values of 0.5, 0.4, and 0.01 M, respectively.


Assuntos
Archaea/enzimologia , Bactérias/enzimologia , Endopeptidases/genética , Endopeptidases/metabolismo , Sequência de Aminoácidos , Ácido Aspártico Endopeptidases , Endopeptidases/isolamento & purificação , Insulina/metabolismo , Cinética , Dados de Sequência Molecular , Pepsina A/metabolismo , Inibidores de Proteases/farmacologia , Especificidade por Substrato , Temperatura , Ureia/farmacologia
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