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1.
Asparaginyl endopeptidase is a cysteine endopeptidase that has strict substrate specificity toward the carboxy side of asparagine residues. Vigna mungo processing enzyme 1, termed VmPE-1, occurs in the cotyledons of germinated seeds of V. mungo, and is possibly involved in the post-translational processing of a vacuolar cysteine endopeptidase, designated SH-EP, which degrades seed storage protein. VmPE-1 also showed a substrate specificity to asparagine residues, and its enzymatic activity was inhibited by NEM but not E-64. In addition, purified VmPE-1 had a potential to process the recombinant SH-EP precursor to its intermediate in vitro. cDNA clones for VmPE-1 and its homologue, named VmPE-1A, were identified and sequenced, and their expressions in the cotyledons of V. mungo seedlings and other organs were investigated. VmPE-1 mRNA and SH-EP mRNA were expressed in germinated seeds at the same stage of germination although the enzymatic activity of VmPE-1 rose prior to that of SH-EP. The level of VmPE-1A mRNA continued increasing as germination proceeded. In roots, stems and leaves of fully grown plants, and in hypocotyls, VmPE-1 and VmPE-1A were little expressed. We discuss possible functions of VmPE-1 and VmPE-1A in the cotyledons of germinated seeds.  相似文献   

2.

Introduction

We examined the acute effects of neutral endopeptidase inhibitor on the hemodynamics and electrical properties of dogs subjected to rapid atrial pacing.

Methods

Ten beagle dogs were used and divided into two groups with and without candoxatril, a neutral endopeptidase inhibitor preadministration. Before and after the 6 hours rapid atrial pacing from the right atrial appendage, the hemodynamics, atrial effective refractory period, and monophasic action potential duration of the right atrial appendage were measured and blood samples were collected. Atrial tissue was also excised after the experiment.

Results

Candoxatril significantly increased plasma ANP levels (Control: 88.4 ± 50.25 vs. Candoxatril: 197.1 ± 32.09 pg/ml, p = 0.004) and prevented reductions in atrial effective refractory period and monophasic action potential duration. We further demonstrated that the treated animals exhibited significantly higher levels of atrial tissue cyclic GMP (Control: 28.1 ± 1.60 fmol/mg vs. Candoxatril: 44.5 ± 12.28 fmol/mg, p = 0.034) as well as that of plasma cyclic GMP (Control: 32 ± 5.5 vs. Candoxatril: 42 ± 7.1 pg/ml, p = 0.028).

Conclusion

Candoxatril suppressed the shortening of atrial effective refractory period and monophasic action potential duration in the rapid atrial pacing model. As plasma ANP and the atrial tissue levels of cyclic GMP were higher in the Candoxatril group than the control, this effect was considered to appear through the reduction of calcium overload caused by ANP and cyclic GMP.  相似文献   

3.
4.
Asparaginyl endopeptidase (AEP) is an endo/lysosomal cysteine endopeptidase with a preference for an asparagine residue at the P1 site and plays an important role in the maturation of toll-like receptors 3/7/9. AEP is known to undergo autoproteolytic maturation at acidic pH for catalytic activation. Here, we describe crystal structures of the AEP proenzyme and the mature forms of AEP. Structural comparisons between AEP and caspases revealed similarities in the composition of key residues and in the catalytic mechanism. Mutagenesis studies identified N44, R46, H150, E189, C191, S217/S218 and D233 as residues that are essential for the cleavage of the peptide substrate. During maturation, autoproteolytic cleavage of AEP''s cap domain opens up access to the active site on the core domain. Unexpectedly, an intermediate autoproteolytic maturation stage was discovered at approximately pH 4.5 in which the partially activated AEP could be reversed back to its proenzyme form. This unique feature was confirmed by the crystal structure of AEPpH4.5 (AEP was matured at pH 4.5 and crystallized at pH 8.5), in which the broken peptide bonds were religated and the structure was transformed back to its proenzyme form. Additionally, the AEP inhibitor cystatin C could be digested by the fully activated AEP, but could not be digested by activated cathepsins. Thus, we demonstrate for the first time that cystatins may regulate the activity of AEP through substrate competition for the active site.  相似文献   

5.
The cerebrospinal fluid (CSF) provides a ready access into the health state of the central nervous system, and alterations in some CSF proteins have been documented in brain disease. However, the complete variety of proteins is not known and methods to identify protein components are still being developed. The goal of this study was to examine the sequence coverage obtained from human CSF digests produced with different proteases. Enzymatic digests of CSF proteins were obtained with arginine-C endopeptidase (ArgC), glutamic acid endopeptidase (GluC), chymotrypsin, trypsin and their combinations, and then examined using reverse phase chromatography and a Finnigan LTQ linear ion trap mass spectrometer. Peptide sequences were identified with BioWorks 3.1 and sequence coverage calculated for the 38 most confidently identified proteins. Trypsin and GluC yielded greater coverage than chymotrypsin, while ArgC had the least sequence coverage. Protein sequence coverage was affected only slightly over four orders of magnitude dynamic range of abundance. Combining the peptides derived from different proteases further increased the coverage. Maximal sequence coverage was achieved by combining digest results from both GluC and trypsin. These results have implications for future studies to identify CSF proteins and their post-translational modifications.  相似文献   

6.
The 13-residue peptide, χ-conotoxin MrIA extracted from the venom of Conus marmoreus, is a potent and selective inhibitor of the human noradrenaline transporter (NET). With the aim of improving its biophysical properties, chemical modifications were performed including the attachment of a lipophilic amino acid at the N-terminus and cyclisation of the peptide backbone with functionality introduced into the linker. All χ-conotoxin MrIA analogues were assembled on solid phase by highly optimised Boc chemistry and N- to C-cyclic analogues accessed by cysteine-mediated intramolecular native chemical ligation. In vitro biological activity at the human NET was evaluated by functional assays. All analogues inhibited the uptake of [3H]noradrenaline with comparable potencies to that of the native peptide, with one of the analogues, the linear N-terminal aminotetradecanoyl MrIA showing a 3-fold increase in potency (p < 0.05).  相似文献   

7.
8.
    
The black‐eyed pea trypsin and chymotrypsin inhibitor (BTCI) is a Bowman–Birk‐type inhibitor from Vigna unguiculata seeds. A complex of BTCI with bovine β‐trypsin was crystallized by the hanging‐drop vapour‐diffusion method with ammonium sulfate as precipitant. Crystals belong to the orthorhombic space group P212121, with unit‐cell parameters a = 59.3, b = 61.8, c = 80.0 Å. Diffraction data were collected to 2.36 Å resolution and were processed to give an overall Rsym of 0.137. The Matthews coefficient for one complex per asymmetric unit is 2.2 Å3 Da−1, with a corresponding solvent content of 43%. After molecular replacement and initial refinement, the model gives an Rcryst of 0.361 and an Rfree of 0.432.  相似文献   

9.
A trypsin inhibitor was isolated from finger millet (Eleusine coracana) by ammonium sulphate fractionation, chromatography on CM-Sephadex and Sepha  相似文献   

10.
    
Trypsin inhibitors have been found in various animals, plants and microorganisms.There were two types of trypsin inhibitors in soybean including Bowman-Birk protease inhibitors(BBI) and Kunitz in-hibitors(KTI).The different BBI genes from wild soybean(G.soja) and cultivated soybean(G.max) formed a multigene family.We constructed a cDNA library of cultivar 'SuiNong 14' seed at the R7 growth stage using the SMART Kit.Seventeen contigs or singletons were highly homologous to soy-bean protease inhibitors.Contigs of 5, 35, 8 and 9 were highly homologous to BBI family members BBI-A1, BBI-A2, BBI-C and BBI-D, respectively.Sequence analyses showed there were novel allelic varia-tions among the 4 BBI members in SuiNong 14.Based on the comparison of soybean seed cDNA li-braries from different developmental stages, it was apparent that the expression of trypsin inhibitors increased during seed development in soybean.Phylogenetic analysis of BBI gene sequences among dicotyledonous and monocotyledonous plants demonstrated that these genes shared a common pro-genitor.  相似文献   

11.
糖尿病及其并发症严重影响人类健康和生活质量,其发病人数呈逐年上升趋势。目前市场糖尿病药物如二甲双胍等小分子化学药以及胰岛素、胰高血糖素样肽1(GLP-1)受体激动剂等多肽药物在一定程度上控制患者血糖水平,但预防和治疗效果仍然不理想。新型理想的糖尿病治疗药物一直都是市场需求和研究热点。抑制剂胱氨酸结(inhibitor cystine knot,ICK)模式多肽是一类多功能环肽,具有三对保守的二硫键(C3-C20、C7-C22和C15-C32)形成紧凑的“结”结构,可以抵抗消化道蛋白酶的降解。近期研究显示,豆科植物来源的ICK模式多肽包括PA1b、Aglycin、Vglycin、Iglycin、Dglycin和aM1等,在细胞水平和动物水平展现出良好的糖脂代谢功能。机制上,ICK模式多肽通过激活胰岛素受体(insulin receptor,IR)/AKT信号通路促进肌肉和肝脏对葡萄糖利用,同时改善胰岛素抵抗,通过激活PI3K/AKT/Erk信号通路修复胰腺功能,从而降低血糖。鉴于ICK模式多肽的生物稳定性和降糖功效满足口服药物商业化要求,在理论上可以开发成天然口服糖尿病多肽药物。本文综述了ICK模式多肽的结构特性、调节糖脂代谢活性及机制的最新研究进展,为糖尿病口服多肽类新药开发提供参考。  相似文献   

12.
    
Porcine pancreatic elastase (PPE) resembles the attractive drug target leukocyte elastase, which has the ability to degrade connective tissue in the body. The crystal structure of PPE complexed with a novel trimacrocyclic peptide inhibitor, FR901451, was solved at 1.9 Å resolution. The inhibitor occupied the subsites S3 through S3′ of PPE and induced conformational changes in the side chains of Arg64 and Arg226, which are located at the edges of the substrate‐binding cleft. Structural comparison of five PPE–inhibitor complexes, including the FR901451 complex and non‐ligated PPE, reveals that the residues forming the S2, S1, S1′ and S2′ subsites in the cleft are rigid, but the two arginine residues playing a part in the S3 and S3′ subsites are flexible. Structural comparison of PPE with human leukocyte elastase (HLE) implies that the inhibitor binds to HLE in a similar manner to the FR901451–PPE complex. This structural insight may help in the design of potent elastase inhibitors.  相似文献   

13.
    
The structure of tick anticoagulant peptide (TAP) has been determined by X-ray crystallography at 1.6 A resolution complexed with bovine pancreatic trypsin inhibitor (BPTI). The TAP-BPTI crystals are tetragonal, a = b = 46.87, c = 50.35 A, space group P41, four complexes per unit cell. The TAP molecules are highly dipolar and form an intermolecular helical array along the c-axis with a diameter of about 45 A. Individual TAP units interact in a head-to-tail fashion, the positive end of one molecule associating with the distal negative end of another, and vice versa. The BPTI molecules have a uniformly distributed positively charged surface that interacts extensively through 14 hydrogen bonds and two hydrogen bonded salt bridges with the helical groove around the helical TAP chains. Comparing the structure of TAP in TAP-BPTI with TAP bound to factor Xa(Xa) suggests a massive reorganization in the N-terminal tetrapeptide and the first disulfide loop of TAP (Cys5T-Cys15T) upon binding to Xa. The Tyr1(T)OH atom of TAP moves 14.2 A to interact with Asp189 of the S1 specificity site, Arg3(T)CZ moves 5.0 A with the guanidinium group forming a cation-pi-electron complex in the S4 subsite of Xa, while Lys7(T)NZ differs in position by 10.6 A in TAP-BPTI and TAP-Xa, all of which indicates a different pre-Xa-bound conformation for the N-terminal of TAP in its native state. In contrast to TAP, the BPTI structure of TAP-BPTI is practically the same as all those of previously determined structures of BPTI, only arginine and lysine side-chain conformations showing significant differences.  相似文献   

14.
    
Interleukin‐5 receptor α is a therapeutic target for hypereosinophilic diseases including allergic inflammations and asthma. The cyclic peptide AF17121 (Ac‐VDE[CWRIIASHTWFC]AEE‐CONH2) has been identified as a submicromolar inhibitor of interleukin 5 (IL5)‐interleukin 5 receptor α (IL5Rα) interaction from a random peptide screen. However, this inhibitor has limitations as a drug lead because of its relatively large size. We used chemical synthesis of peptides with natural and non‐natural amino acids along with kinetic binding and cell proliferation competition assays to expand definition of structural elements in the peptide that are important for receptor antagonism and to elucidate the underlying pharmacophore. We found that the specific steric array of hydrogen bonding groups in the Arg 6 guanido side chain is critical for receptor inhibition. We also investigated noncharged structural elements in AF17121. Screening a set of five hydrophobic residues showed that peptide function is strongly sensitive to variations in several of these residues, most prominently Ile 7 and Trp 13. We postulate that presentation of charged, hydrogen bonding and hydrophobic structural elements within the disulfide‐constrained peptide drives IL5Rα recruitment by AF17121. We hypothesize from these results and previous receptor mutagenesis studies that Arg 6 recruitment of IL5Rα occurs through hydrogen bonding as well as charge–charge interactions with Asp 55 in site one of domain 1 of IL5Rα, and that this interaction is complemented by additional charged and hydrophobic interactions around the Asp 55 locus. Scaffolding a limited set of structural elements in the inhibitor pharmacophore may be useful for small molecule antagonist design inspired by the peptide. © 2006 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 88:83–93, 2007. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com.  相似文献   

15.
    
Trypsin inhibitor SFTI-1 isolated from sunflower seeds (comprising 14 amino acid residues and two cycles: head-to-tailcyclisation and disulfide bridge) is the smallest naturally occurring plant serine proteinase inhibitor. In our recent paperwe have shown that the elimination head-to-tail cyclisation did not change trypsin inhibitory activity as judged by measuredby association equilibrium constants Ka. The removal of disulfide bridge produced 2.4-fold lower activity. In the present paper we described chymotrypsin inhibitory activity. SFTI-1 inhibits significantly lower bovine -chymortypsin(Ka = (5.20±1.56) × 106 M-1). The activity of the analogue with disulfide bridge only was practically the same, whereas the Ka value determined forhomodetic peptide was almost 3-fold lower. Considering the results obtained and the recent literature data we postulate thelower inhibitory activity against both enzyme of the analogue with head-to-tail cyclisation only reflect its lower proteolytic stability.  相似文献   

16.
Summary Trypsin inhibitor SFTI-1 isolated from sunflower seeds (comprising 14 amino acid residues and two cycles: head-to-tail cyclisation and disulfide bridge) is the smallest naturally occurring plant serine proteinase inhibitor. In our recent paper we have shown that the elimination head-to-tail cyclisation did not change trypsin inhibitory activity as judged by measured by association equilibrium constants K a . The removal of disulfide bridge produced 2.4-fold lower activity. In the present paper we described chymotrypsin inhibitory activity. SFTI-1 inhibits significantly lower bovine α-chymortypsin (K a =(5.20±1.56)×106 M−1). The activity of the analogue with disulfide bridge only was practically the same, whereas the K a value determined for homodetic peptide was almost 3-fold lower. Considering the results obtained and the recent literature data we postulate the lower inhibitory activity against both enzymes of the analogue with head-to-tail cyclisation only reflect its lower proteolytic stability.  相似文献   

17.
Two forms of urinary trypsin inhibitor (UTI-1 and UTI-2) were purified from pooled urine of normal male rats to apparent homogeneity by salting out, affinity chromatography, gel filtration, and reverse-phase HPLC. UTIs-1 and 2 were shown to be thermostable glycoproteins with the respective molecular weights of 22,000 and 18,000 estimated by SDS-PAGE. These inhibitors combined with bovine trypsin in a 1:1 molar ratio: the K d values were 2.5 × 10–10 and 2.3 × 10–10 M, respectively. Amino acid composition and sequence analysis indicated that UTI-1 corresponded to rat bikunin of which the amino acid sequence was deduced from a rat liver cDNA clone encoding 1-microglobulin [Lindqvist et al. (1992), Biochim. Biophys. Acta 1130, 63–67] except that the protein sequence seemed to lack C-terminal serine, and UTI-2 corresponded to UTI-1 lacking N-terminal 21 amino acid residues.  相似文献   

18.
Two novel nematicidal cyclodepsipeptides, designated bursaphelocides A and B, were isolated from the culture filtrate of an imperfect fungus, strain D1084, belonging to Mycelia sterilia. Bursaphelocide A (1), containing 2-hydroxy-3-methylpentanoic acid, proline, isoleucine, N-methylalanine, N-methylvaline, and β-alanine in sequence, and bursaphelocide B (2), comprising 4-methylproline instead of proline in 1, are novel 2-hydroxy-3-methylpentanoic acid analogues of insecticidal destruxins.  相似文献   

19.
    
We have characterized in vitro and in vivo effects of trypsin inhibitors from Theobroma seeds on the activity of trypsin- and chymotrypsin-like proteins from Lepidopteran pest insects. The action of semipurified trypsin inhibitors from Theobroma was evaluated by the inhibition of bovine trypsin and chymotrypsin activities determined by the hydrolysis of N-Benzoyl-DL-Arginine-p-Nitroanilide (BAPA) and N-Succinyl-Ala-Ala-Pho-Phe p-Nitroanilide (S-(Ala)2ProPhe-pNA). Proteinase inhibitor activities from Theobroma cacao and T. obovatum seeds were the most effective in inhibiting trypsin-like proteins, whereas those from T. obovatum and T. sylvestre were the most efficient against chymotrypsin-like proteins. All larvae midgut extracts showed trypsin-like proteolytic activities, and the putative trypsin inhibitors from Theobroma seeds significantly inhibited purified bovine trypsin. With respect to the influence of Theobroma trypsin inhibitors on intact insects, the inclusion of T. cacao extracts in artificial diets of velvet bean caterpillars (Anticarsia gemmatalis) and sugarcane borer (Diatraea saccharalis) produced a significant increase in the percentage of adult deformation, which is directly related to both the survival rate of the insects and oviposition.  相似文献   

20.
Using the X-ray structure of the complex of bovine β-trypsin with the basic pancreatic trypsin inhibitor, the hydrogen-bond structure consisting of Ser195, His57 and Asp102 is clarified in relation to the mechanism of the enzymatic reaction from an ab initio quantum chemical point of view. Under the influence of the inhibitor, of the three hydrogen bonds involving Ser214, His57 and Ala56 around Asp102, and of the other ionic amino acid residues, Asp102 plays a significant role in lowering the barrier height of the proton transfer from Ser195 to His57 without accepting a proton from His57. The principal cause of the barrier height lowering is the electrostatic interaction.  相似文献   

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