Grafting analysis indicates that malfunction of TRICOT in the root causes a nodulation-deficient phenotype in Lotus japonicus

Leguminous plants develop root nodules in symbiosis with soil rhizobia. Nodule formation occurs following rhizobial infection of the host root that induces dedifferentiation of some cortical cells and the initiation of a new developmental program to form nodule primordia. In a recent study, we identified a novel gene, TRICOT (TCO), that acts as a positive regulator of nodulation in Lotus japonicus. In addition to its role in nodulation, tco mutant plants display pleiotropic defects including abnormal shoot apical meristem formation. Here, we investigated the effect of the tco mutation on nodulation using a grafting approach. The results strongly indicate that the nodulation-deficient phenotype of the mutant results from malfunction of the TCO gene in the root.     

Effect of Substrate Concentration on Plastein Productivity and Some Rheological Properties of the Products

A bacterial arginase was purified to homogeneity from a strain of Bacillus brevis. The native enzyme, with an estimated MW of 143,000, migrated on SDS-PAGE as a single polypeptide of estimated MW of 33,000. The enzyme, highly specific to l-arginine, showed the maximum activity at pH 11.0 in the presence of Mn²⁺ ions and the pI was 4.8 by isoelectric focusing. The enzyme activity was increased significantly by the addition of Mn²⁺, Ni²⁺, or Co²⁺ ions, and inhibited potently by chemicals such as HgCl₂, N-bromosuccinimide, or glutathione. The K_ms for l-arginine and l-canavanine were 0.69 and 22.2 mm, respectively. The enzyme was inhibited competitively by γ-guanidinobutyric acid, and non-competitively by l-lysine, l-ornithine, creatine, blasticidin S, and edeine B₁ Analysis of the N-terminal amino acid sequence of the purified bacterial enzyme found 33–36% homologies with the Agrobacterium, yeast, rat, and human enzymes.     

Diverse role of conformational dynamics in carboxypeptidase A-driven peptide and ester hydrolyses: disclosing the "perfect induced fit" and "protein local unfolding" pathways by altering protein stability

Catalytic mechanisms of carboxypeptidase A (CPA) are well known for their diversity and the relative inaccessibility for a decisive comprehension. Recent encouraging attempts through modern computational techniques promoted new challenges for the complementary experimental endeavors. In this work, we have applied the stopped-flow technique and the method of reaction progress curve fitting to extract kinetic parameters for the CPA-catalyzed hydrolyses of smaller (typical) peptide and ester substrates, known for their strong activating/inhibiting impact, thus to which the traditional method of "initial rates" is not applicable. Our approach that innately implies the overall constancy of the affecter (substrate plus "active" product) concentration, made it possible to rigorously determine the physically meaningful "effective" values for the catalytic and Michaelis constants under diverse experimental conditions including variable temperature and urea or trimethylamine N-oxide concentrations. Analysis of the obtained results allowed for: (i) the further substantiation of diverse mechanistic patterns for archetypal specific peptide and ester substrates, (ii) testing and disclosure of intrinsic links between the stabilizing/destabilizing and activating/inhibiting effects for the important model enzyme, CPA, and (iii) tentative explanation of a distinct activating/inhibiting impact of these substrates through the strong specific interaction of their benzyl (Bz) moiety with the substrate binding S(3) subsite of CPA. We have demonstrated that stabilization of CPA either through the interaction with an extra Bz moiety (belonging to another substrate or to the product) leads to the increase of its catalytic power with respect to the specific peptide substrate and to its decrease with respect to the counterpart ester substrate. We conjecture that the catalytic mechanisms operating in these two cases include: (a) the "promoted water" mechanism for the peptide substrate that, seemingly, provides the almost "perfect induced fit" (low-barrier conformational adaptation), and (b) presumably, the "anhydride intermediate" mechanism for the ester substrate that, anyway, requires substantial conformational rearrangement (in fact, "partial or local unfolding") of the protein environment in the course of the rate-determining step.     

Development of leucine aminopeptidase activity during daylily flower growth and senescence

The possibility that exopeptidases, i.e. aminopeptidases and carboxypeptidases, in addition to the previously studied endopeptidase might also be developmentally regulated in daylily petals was examined. The level of leucine aminopeptidase and endopeptidase activities changed after the flower was fully open while that of carboxypeptidase activity remained relatively unchanged throughout senescence. Leucine aminopeptidase activity seemed to increase after the flower was fully open and peaked several hours earlier than endopeptidase did. Taken together, it is postulated that leucine aminopeptidase might play a role in protein turnover during flower opening and in the initiation of protein hydrolysis associated with petal senescence while the endopeptidase could be responsible for the breakdown of the bulk of proteins at the later stages. The drop in leucine aminopeptidase activity associated with the onset of daylily petal senescence was effectively halted by a cycloheximide treatment of cut daylily flowers for 24 h which was previously shown to prolong the vase life of the flowers and prevent protein loss from the petals. Apart from both being developmentally regulated in daylily petals, the leucine aminopeptidase activity and the previously studied endopeptidase are different in several aspects. They appear to have different pH optima, 8 for leucine aminopeptidase and 6.2 for endopeptidase. Unlike the endopeptidase activity, no new leucine aminopeptidase isozymes appeared during petal senescence, and the leucine aminopeptidase did not appear to belong to the cysteine class of proteolytic enzymes.     

Purification and characterization of a high molecular mass serine carboxypeptidase from <Emphasis Type="Italic">Monascus pilosus</Emphasis>

Two serine carboxypeptidases, MpiCP-1 and MpiCP-2, were purified to homogeneity from Monascus pilosus IFO 4480. MpiCP-1 is a homodimer with a native molecular mass of 125 kDa composed of two identical subunits of 61 kDa, while MpiCP-2 is a high mass homooligomer with a native molecular mass of 2,263 kDa composed of about 38 identical subunits of 59 kDa. This is unique among carboxypeptidases and distinguishes MpiCP-2 as the largest known carboxypeptidase. The two purified enzymes were both acidic glycoproteins. MpiCP-1 has an isoelectric point of 3.7 and a carbohydrate content of 11%, while for MpiCP-2 these values were 4.0 and 33%, respectively. The optimum pH and temperature were around 4.0 and 50°C for MpiCP-1, and 3.5 and 50°C for MpiCP-2. MpiCP-1 was stable over a broad range of pH between 2.0 and 8.0 at 37°C for 1 h, and up to 55°C for 15 min at pH 6.0, but MpiCP-2 was stable in a narrow range of pH between 5.5 and 6.5, and up to 50°C for 15 min at pH 6.0. Phenylmethylsulfonylfluoride strongly inhibited MpiCP-1 and completely inhibited MpiCP-2, suggesting that they are both serine carboxypeptidases. Of the substrates tested, benzyloxycarbonyl-l-tyrosyl-l-glutamic acid (Z-Tyr-Glu) was the best for both enzymes. The K_m, V_max, K_cat and K_cat/K_m values of MpiCP-1 for Z-Tyr-Glu at pH 4.0 and 37°C were 1.33 mM, 1.49 mM min^–1, 723 s^–1 and 545 mM^–1 s^–1, and those of MpiCP-2 at pH 3.5 and 37°C were 1.55 mM, 1.54 mM min^–1, 2,039 s^–1 and 1,318 mM^–1 s^–1, respectively.     

Prostate targeting ligands based on N-acetylated alpha-linked acidic dipeptidase

To identify inhibitors of the intrinsic N-acetylated alpha-linked acidic dipeptidase (NAALADase) activity of prostate specific membrane antigen (PSMA) that may be useful for targeting imaging agents or chemotherapeutic drugs to disseminated prostate cancer, analogs of the tetrahedral transition state for hydrolysis of the natural substrate, N-acetylaspartylglutamate (NAAG), were synthesized. These compounds were assayed for their ability to inhibit the membrane-associated enzyme isolated from LNCaP prostate cancer cells. Active inhibitors were further assayed for their cytotoxicity and membrane binding. We have identified nine compounds, including fluorescent and iodine-labeled conjugates, which inhibit NAALADase enzyme activity with IC(50)s at, or below, 120nM. The binding of these compounds to the cell surface of viable LNCaP prostate tumor cells appears to be specific and saturable, and none of the compounds alter the cell cycle kinetics or induce apoptosis in LNCaP cells, suggesting that they are relatively innocuous and are suitable for targeting imaging agents or cytotoxic drugs to disseminated prostate cancer.     

老年支气管哮喘患者血清MC-CP、Th17的表达及其与呼吸功能、肺功能的相关性分析

摘要 目的：探究老年支气管哮喘患者血清肥大细胞羧肽酶（MC-CP）、Th17表达及其与患者呼吸功能、肺功能的相关性。方法：选择2018年4月至2021年8月于中国人民解放军东部战区总医院接受治疗的120例老年支气管哮喘患者为研究组（SG）,另选同期于我院接受治疗的100例支气管炎患者为对照组（CG）,对比两组患者血清MC-CP、Th-17、呼气峰值流速（PEF）、第1秒用力呼气量（FEV₁）、血氧分压（PaO₂）、FEV₁占预计值的百分数（FEV₁/FVC）差异,就研究组患者MC-CP、Th-17水平与其呼吸功能、肺功能的相关性开展Spearman分析。结果：（1）研究组患者的MC-CP水平明显高于对照组,Th17百分比同样明显高于对照组（P<0.05）;（2）研究组患者的呼吸功能指标PEF、PaO₂,以及肺功能指标FEV₁、FEV₁/FVC均明显低于对照组（P<0.05）;（3）研究组患者MC-CP与PEF、PaO₂呈现明显负相关联系（r=-0.558、-0.700,P<0.001）,研究组患者Th17与PEF、PaO₂呈现明显负相关联系（r=-0.695、-0.774,P<0.001）;（4）研究组患者MC-CP与FEV₁、FEV₁/FVC呈现明显负相关联系（r=-0.609、-0.481,P<0.001）,研究组患者Th17与FEV₁、FEV₁/FVC呈现明显负相关联系（r=-0.622、-0.561,P<0.001）。结论：老年支气管哮喘患者血清MC-CP及Th17水平会出现异常升高状态,而呼吸功能与肺功能会出现降低,相关性分析显示此类患者血清MC-CP及Th17水平与其呼吸功能、肺功能均呈现负相关联系。     

一种新的B链C端去四肽胰岛素的研制方法

报道了将单体胰岛素前体(MIP)经胰蛋白酶和羧肽酶B两步连续酶切获得B链C端去四肽胰岛素(DTI)的方法。MIP由甲醇酵母表达,最高发酵表达量达到150mg/L。发酵液中MIP通过疏水层析,分子筛初步纯化后直接进行酶切,在胰蛋白酶酶切3h后加入抑制剂paminobenzamidine处理15min,然后直接加入羧肽酶B酶切6h,再通过反相柱纯化即可得到纯品DTI,从分子筛到最后DTI,总纯化得率达到77%。按中国药典小白鼠惊厥法测定得DTI的生物活力为22IU/mg,是胰岛素的80%,在Superdex G-75分子筛上测定DTI的解离聚合曲线,证明其是单体。     

Plasma levels of unactivated thrombin activatable fibrinolysis inhibitor (TAFI) are down-regulated in young adult women: analysis of a normal Japanese population

Thrombin-activatable fibrinolysis inhibitor (TAFI) is an anaphylatoxin-inactivating enzyme generated by proteolytic cleavage of its zymogen, and is the same enzyme as that first designated by our group as procarboxypeptidase R (proCPR). TAFI in plasma is presumed to influence vascular disease in its role as a fibrinolysis inhibitor. The activity of TAFI is strongly influenced by genetic polymorphism, especially at amino acids Thr/Ala-147 and Thr/Ile-325. In this study, we analyzed 202 healthy controls who were not on any medication, had no unusual medical history and whose blood data were normal. In a previous report, we established an enzyme-linked immunosorbent assay (ELISA) specific for non-activated TAFI (proCPR), and investigated levels of unactivated TAFI as an estimate of anti-fibrinolytic capacity. In this study, we determined normal Japanese TAFI levels for each age, sex, and genetic polymorphism of Thr/Ala-147 and Thr/Ile-325, and also showed that the TAFI level in young adult women is lower than in aged women.     

Belactins A and B,New Serine Carboxypeptidase Inhibitors Produced by Actinomycete. I. Taxonomy,Production, Isolation and Biological Actmties

Abstract

Belactins A and B, new inhibitors of serine carboxypeptidase were discovered in the fermentation broth of Saccharopolyspora sp. MK19–42F6. They were purified by ethyl acetate extraction, silica gel chromatography, Sephadex LH20 chromatography, Capcellpak C18 SG120 reversed phase HPLC and centrifugal partition chromatography (CPC) following their inhibitory activity against carboxypeptidase Y (CP-Y). The inhibition constants (K_i) of belactins A and B against CP-Y are 0.14 and 0.27 μM respectively. Belactins A and B have highly specific inhibitory activities for CP-Y among various peptidases, have no antimicrobial activities at 100 μ/ml and have low toxicities.