Investigation of the applicability of cis-urocanic acid as a model for the catalytic Asp–His dyad in the active site of serine proteases based on 1H NMR hydrogen bonding studies and spectroscopic pKa measurements

Neuvonen, Helmi; Neuvonen, Kari

doi:10.1039/a708832i

Cited by 8 publications

(3 citation statements)

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“…The simplest model of the catalytic dyad is probably (2Z)‐3‐(1 H ‐imidazol‐4‐yl)prop‐2‐enoic acid ( cis ‐urocanic acid) 12–16. The rigid structure of this model facilitates the analysis of the OHN hydrogen bridge, but the model does not take the influence of the hydrogen bridge to the serine/cysteine residue into account.…”

Section: Introductionmentioning

confidence: 99%

Costimulatory molecule B7‐H1 in primary and metastatic clear cell renal cell carcinoma

Thompson

Gillett

Cheville

et al. 2005

Cancer

163

116

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BACKGROUNDCancer cell expression of costimulatory molecule B7‐H1 has been implicated as a potent inhibitor of T‐cell–mediated antitumoral immunity. The authors recently reported that B7‐H1 is aberrantly expressed in primary renal cell carcinoma (RCC). Blockade of B7‐H1, as demonstrated in several murine cancer models, now represents a promising therapeutic target in RCC. However, the potential expression of B7‐H1 in metastatic RCC has not been investigated. In the current study, the authors updated their primary RCC results with additional follow‐up and investigated the potential role of B7‐H1 in metastatic RCC.METHODSBetween 2000 and 2004, 196 patients underwent nephrectomy and 26 patients had resection of RCC metastases for clear cell RCC. Immunohistochemical analysis was performed on tumor cryosections using a B7‐H1 monoclonal antibody (clone 5H1). A urologic pathologist quantified the percentage of B7‐H1–positive tumor cells and lymphocytes.RESULTSVariable levels of B7‐H1 were expressed on primary RCC tumor cells (n = 130 [66.3%]) and primary tumor‐infiltrating lymphocytes (n = 115 [58.7%]). Patients with high expression of B7‐H1 on primary tumor cells and/or lymphocytes were significantly more likely to die of RCC compared with patients with low B7‐H1 expression (risk ratio [RR] = 4.17; 95% confidence interval [95% CI], 1.97–8.84; P < 0.001) and this risk persisted in multivariate analysis after adjusting for the Mayo Clinic stage, size, grade, and necrosis score (RR = 2.63; 96% CI, 1.23–5.64; P = 0.013). Of the 26 metastatic specimens, cancer cell and lymphocyte B7‐H1 expression were demonstrated in 17 (65.4%) and 18 (69.2%) specimens, respectively. In total, 14 (54.3%) metastatic specimens had high aggregate B7‐H1 levels compared with 44.4% in primary RCC specimens.CONCLUSIONSPatients with RCC with high B7‐H1 expression were significantly more likely to die even after multivariate analysis. The authors also demonstrated that a high percentage of RCC metastases similarly harbored B7‐H1. The authors surmised that B7‐H1 blockade may augment current immunotherapy, including patients treated for metastases after cytoreductive nephrectomy. Cancer 2005. © 2005 American Cancer Society.

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Section: Introductionmentioning

confidence: 99%

Costimulatory molecule B7‐H1 in primary and metastatic clear cell renal cell carcinoma

Thompson

Gillett

Cheville

et al. 2005

Cancer

163

116

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“…These signals can correspond to the trans -urocanic acid moiety (H-f, H-g) and cis -urocanic acid moiety (H-f′, H-g′). It is known that the 1 H resonances of cis -urocanic acid are significantly different from that for trans -urocanic acid. , In the spectrum of PEI-LA-UA obtained via N -hydroxysuccinimide ester of UA (Figure B), the signals for the protons of cis -urocanic acid moiety were not present.…”

Section: Resultsmentioning

confidence: 96%

“…It is known that the 1 H resonances of cisurocanic acid are significantly different from that for transurocanic acid. 56,57 In the spectrum of PEI-LA-UA obtained via N-hydroxysuccinimide ester of UA (Figure 3B), the signals for the protons of cis-urocanic acid moiety were not present. Figure 4 illustrates the UV absorption spectra of PEI-LA-UA (spectrum A) and UA (spectrum D) recorded at pH 6.4.…”

Section: Synthesis and Characterization Of Acylated Polymersmentioning

confidence: 99%

Ligand-Directed Acid-Sensitive Amidophosphate 5-Trifluoromethyl-2′-Deoxyuridine Conjugate as a Potential Theranostic Agent

et al. 2013

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Herein, we report a novel strategy to engineer an acid-sensitive anticancer theranostic agent using a vector-drug ensemble. The ensemble was synthesized by directly conjugating the linoleic acid (LA)-modified branched polyethyleneimine with a chemotherapeutic drug trifluorothymidine. Linoleic acid residues were grafted onto 25 kDa polyethyleneimine (PEI) by treating PEI with linoleic acid chloroanhydride. 5-Trifluoromethyl-2'-deoxyuridine (trifluorothymidine, TFT) was introduced into LA-PEI conjugate by phosphorylating the conjugate with amidophosphate of trifluorothymidine 5'-monophosphate (pTFT), which had been activated by its conversion into the N,N-dimethylaminopyridine derivative. The extent of mononucleotide analog incorporation in the polymer was regulated by the ratio of pTFT to the polymer during the synthesis. Samples containing 20-70 TFT residues per PEI molecule were obtained. The cytotoxicity of PEI-LA-pTFT conjugates decreased with increasing nucleotide content, as examined using the MTT method. Due to the presence of fluorine atoms, TFT-based conjugates could be detected directly in the animals by (19)F magnetic resonance imaging. In addition, the presence of the amidophosphate group in PEI-LA-pTFT conjugates allowed their detection by in vivo(31)P NMR spectroscopy. Indeed, the (31)P NMR signal of a phosphoramide (δ ~ 12 ppm) was observed in the mouse muscle tissue treated with PEI-LA-pTFT conjugate along with the signals from endogenous phosphorus-containing compounds. At the same time, the use of PEI-LA-pTFT conjugate for chemotherapeutic drug delivery is limited due to the low release of pTFT from the carrier. To enhance the release of the drug from the conjugate in the endosomes, PEI-LA polymer was coupled with urocanic acid (UA), which bears imidazole ring and thus can form an acid-labile P-N bond with pTFT. The PEI-LA-UA-pTFT conjugate containing 30 residues of UA and 40 residues of pTFT was tested against the murine Krebs-II ascites carcinoma, grown as an ascetic tumor. The intraperitoneal injection of the conjugates resulted in prolongation of the animals' life and to the complete disappearance of the tumor after three injections.

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A model study of the efficiency of the Asp–His–Ser triad

Lankau

2010

J Comput Chem

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The observation of the Asp-His-Ser triad (Asp: aspartate, His: histidine, Ser: serine) triad both in mammalian and bacterial proteases suggests a special efficiency. A series of B3LYP/D95*(d,p) calculations on various [X-H(beta)Y](-) dyads (as part of the [X-H(beta)Y-H(alpha)Ac](-) model triad, HAc: acetic acid) made from eight different anions X(-) and 15 different coupling elements H(beta)Y was done to analyze the molecular origin of this efficiency. The X(-) anion acts merely as an electron density donor independent of its chemical nature, and the evolutionary selection of Asp for the catalytic triad therefore seems to be caused by the pH of the triads environment. As the linking proton H(beta) moves from Y(-) to X(-), electron density is effectively moved from X(-) to Y(-) thereby increasing the proton affinity (PA) of the [X-HY](-) dyad, which finally leads to the deprotonization of the HAc molecule. The degree to which the position of H(alpha) controls the PA is dominantly determined by the coupling element HY. The model calculations indicate that 4-methyl-1H-imidazole (HMim) is a very efficient coupling element, which suggest that the evolutionary convergence to the Asp-His-Ser is not only controlled by the ready availability of the imidazole motive in His but also by its high efficiency.

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Investigation of the applicability of cis-urocanic acid as a model for the catalytic Asp–His dyad in the active site of serine proteases based on 1H NMR hydrogen bonding studies and spectroscopic pKa measurements

Cited by 8 publications

References 53 publications

Costimulatory molecule B7‐H1 in primary and metastatic clear cell renal cell carcinoma

Costimulatory molecule B7‐H1 in primary and metastatic clear cell renal cell carcinoma

Ligand-Directed Acid-Sensitive Amidophosphate 5-Trifluoromethyl-2′-Deoxyuridine Conjugate as a Potential Theranostic Agent

A model study of the efficiency of the Asp–His–Ser triad

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