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Biomedical subjects

D Guillerm

Publications and source records attributed to D Guillerm.

At least 19 recordsLinked to original sources
PubMed2001

Synthesis, mechanism of action, and antiviral activity of a new series of covalent mechanism-based inhibitors of S-adenosyl-L-homocysteine hydrolase.

A direct method for the preparation of 5'-S-alkynyl-5'-thioadenosine and 5'-S-allenyl-5'-thioadenosine has been developed. Treatment of a protected 5'-acetylthio-5'-deoxyadenosine with sodium methoxide and propargyl bromide followed by deprotection gave the 5'-S-propargyl-5'-thioadenosine 4. Under controlled base-catalysis with sodium tert-butoxide in tert-butyl alcohol 4 was quantitatively converted into 5'-S-allenyl-5'-thioadenosine 5 or 5'-S-propynyl-5'-thioadenosine 6. Incubation of recombinant human placental AdoHcy hydrolase with 4, 5, or 6 resulted in time- and concentration-dependent inactivation of the enzyme (K(i): 45 +/- 0.5, 16 +/- 1, and 15 +/- 1 microM, respectively). Compound 4 caused complete conversion of the enzyme from its E-NAD(+) to E-NADH form during the inactivation process. This indicates that 4 is a substrate for the 3'-oxidative activity of AdoHcy hydrolase (type I inhibitor). In contrast, the NAD(+)/NADH content of the enzyme was not affected during the inactivation process with 5 and 6, and their mechanism of inactivation was further investigated. Addition of enzyme-sequestered water on the S-allenylthio group of 5 or S-propynylthio group of 6 within the active site should lead to the formation of the corresponding thioester 7. This acylating-intermediate agent could then undergo nucleophilic attack by a protein residue, leading to a type II mechanism-based inactivation. ElectroSpray mass spectra analysis of the inactivated protein by 5 supports this mechanistic proposal. Further studies (MALDI-TOF and ESI/MS(n) experiments) of the trypsin and endo-Lys-C proteolytic cleavage of the fragments of inactivated AdoHcy hydrolase by 5 were carried out for localization of the labeling. The antiviral activity of 4, 5, and 6 against a large variety of viruses was determined. Significant activity (EC(50): 1.9 microM) was noted with 5 against vaccinia virus.

Adenosylhomocysteinase↗
PubMed1998

The catalytic mechanism of adenosylhomocysteine/methylthioadenosine nucleosidase from Escherichia coli--chemical evidence for a transition state with a substantial oxocarbenium character.

The substrate and inhibitory specificity of Escherichia coli adenosylhomocysteine (AdoHcy)/methylthioadenosine (MeSAdo) nucleosidase has been explored with several MeSAdo analogues modified on the sugar moiety at the 2', 3' and 5' positions. Alteration at C3' or at C2' and C3' positions in MeSAdo abolished substrate activity. However, the 2'-deoxy analogue of MeSAdo is effective as a substrate; this result provides evidence against a possible general-base catalysis involving the anchimeric assistance of the 2'-alpha-hydroxy group and the formation of a 1,2-epoxide as an intermediate in the catalytic process. The results of a study of the interaction of an 8,5'-cyclo analogue of MeSAdo with the enzyme indicate the importance of the glycosidic conformation of the substrate for binding to the active site. The enzyme discriminates against methanol attack from the solvent during catalysis. This implies the participation of an enzyme-directed water nucleophile. A poor solvent kinetic deuterium-isotope effect was measured (0.93) on the Vmax. Plots of log Vmax and log (Vmax/Km) for MeSAdo as a function of pH values from 5.0 to 8.5 are similar, with two presumably essential ionisable groups for catalysis with apparent pKa values of 5.6 and 8.2, whereas Km is independent of pH. When the 2'-alpha-hydroxy group of MeSAdo is substituted by fluorine, a significant decrease (28 500-fold) in the Vmax for enzyme-catalysed hydrolysis of the modified substrate is observed. This result indicates a transition state with a substantial oxocarbenium character. From these data, the reaction mechanism for AdoHcy/MeSAdo nucleosidase is discussed.

Catalysis↗
PubMed1998

A new series of cyclic amino acids as inhibitors of S-adenosyl L-methionine synthetase.

Optically active 3-amino-3-(tetrahydrofuranyl) carboxylic acid, 3-amino-3-(tetrahydrothienyl) carboxylic acid and their corresponding six membered ring analogues have been synthesised and examined as potential inhibitors of the enzyme S-adenosylmethionine (AdoMet) synthetase. The kinetic behaviour of these compounds was studied using recombinant rat liver AdoMet synthetase (alpha-isoform) fractionated from E. coli transformed with the plasmid pSSRL-T7N. All the compounds tested were competitive inhibitors of the enzyme with respect to L-methionine.

Amino Acids, Cyclic↗
PubMed1998

The mechanism of inactivation of S-adenosylhomocysteine hydrolase by fluorinated analogs of 5'-methylthioadenosine.

5'-Deoxy-5'-difluoromethylthioadenosine (DFMTA) 1a and 5'-deoxy-5'-trifluoromethyl-thioadenosine (TFMTA) 1b are inhibitors of beef liver S-adenosyl-L-homocysteine hydrolase. DFMTA and TFMTA are time-dependent and irreversible inhibitors of the enzyme. Both 1a and 1b are oxidized by E-NAD+ to produce E-NADH and fluoride anion is formed in the inactivation reaction (2.2 mol of fluoride/mole of enzyme subunit and 3.1 fluoride/mole of enzyme subunit from DFMTA and TFMTA respectively). Using [8-3H]-1a or [8-3H]-1b no trace of labelled adenosine was detected during the inactivation reaction but adenine was formed. The mechanism of inhibition of S-adenosyl-L-homocysteine hydrolase by these two fluorinated nucleosides is discussed.

Adenosine↗
PubMed1998

A new series of S-adenosyl-L-methionine synthetase inhibitors.

A new series of epithio and epoxy amino acid analogues of L-methionine or L-methoxinine were examined as potential inhibitors of the enzyme S-adenosylmethionine (AdoMet) synthetase. The kinetic behaviour of these compounds was studied using recombinant rat liver S-adenosyl-L-methionine sythetase (alpha-isoform) fractionated from E. coli, transformed with the plasmid pSSRL-T7N. All the compounds tested were competitive inhibitors with respect to L-methionine and the (2S, 4S)-2-amino-4,5-epoxy pentanoic acid was found to be a very potent inhibitor of the enzyme compared to those already reported for AdoMet synthetase from other mammalian tissues.

Animals↗
PubMed1985

Preoperative chemotherapy in epidermoid bronchogenic carcinoma.

Palliative chemotherapy in cases of epidermoid bronchogenic carcinoma, initially judged to be inoperable, made it possible to perform operative resection in 50 cases. An association of cis-platinum and bleomycin was used, this combination having previously been considered synergistic. In certain cases the tumour seemed to have disappeared on macroscopic examination of the resected specimen, and in some instances no tumoral cells could be found on histological examination. This series brought out several positive features: chemotherapy made it possible to operate on patients previously judged to be inoperable; it ensured maximum local efficiency of drugs because of the absence of abnormal vascularity; and it made it possible to anticipate the cure of occult metastases. However, three negative aspects were also present: modification of postoperative TNM classification making it difficult to establish a prognosis; difficulty in determining therapeutic strategy for pNo; and inadequate long-term follow-up. On the whole the positive points appeared to outweigh the negative aspects, but a randomized study is necessary to confirm this.

Adult↗
PubMed1985

Immunological effect of silica dust analyzed by monoclonal antibodies.

We found a significant decrease of OKT8 + ve cells in silicosis patients (18.1%), but also in unaffected exposed workers (19.0%), when compared with sex- and age-matched controls (22.8%). The proportion of OKT8 + ve cells was significantly lower in subjects with antinuclear antibodies (15.7%) and in those with IgG-rheumatoid factors (16.3%).

Adult↗
PubMed1984

Surgery and chemotherapy. A new method of treatment for squamous cell bronchial carcinoma.

Between April, 1981, and December, 1982, 32 patients with squamous cell bronchial carcinoma were treated with a chemotherapy regimen followed by operation. The preoperative chemotherapeutic agents used were cisplatin, bleomycin, and mitomycin C. A thoracotomy was performed 3 to 4 weeks after the last day of the last treatment. Of the 29 undergoing resection, three (10.3%) had no tumor cells in the resected specimen and four (12.5%) had only a few neoplastic microcenters in tissue necrosis or fibrosis. We suggest that the use of this new chemotherapy combination with surgical resection provides excellent palliation, increases resectability, and has a potential for increasing the cure rate in squamous cell carcinoma of the lung.

Adult↗
PubMed1983

[Influence of the localization on the prognostic value of E, E-active and autologous rosettes in lung, esophagus and otorhinolaryngologic cancer].

E, E-active and autologous-rosette-forming-lymphocytes (E, Eact-, auto-RFC) were studied in 66 patients with lung cancer (2 stage I, 17 stage II, 20 stage III, 27 stage IV), 42 patients with head and neck cancer (14 stage III, 28 stage IV) and 22 patients with esophagus cancer (11 stage II, 6 stage III, 5 stage IV). Compared to controls, E-RFC were found to be depressed in each of the three different localizations (p less than 0.001), Eact-RFC were found to be depressed in head and neck as well as esophagus cancer (p less than 0,05 and p less than 0,01 respectively) and auto-RFC were found to be depressed in lung and esophagus cancer (p less than 0,01). Mean survival times of patients with RFC over and under 1 SD below the average value were compared. Significant differences were demonstrated in E-RFC and auto-RFC for head and neck cancer and in Eact-RFC for lung cancer.

Adult↗
PubMed1982

[Prognostic significance of lymphocytes forming "active rosettes" in lung cancer].

Lymphocytes forming E rosettes, active E, autologous and EA antibodies were studied in 66 subjects (56 men, 10 women, mean age 59, range: 40-85 years) who presented with lung cancer classified on the TMN scale in stages I and II: 19; stage III: 20; stage IV: 27. In comparison to the controls, there was a significant reduction (p less than 0.01) in E, autologous and EA rosettes in the patients. A reduction in E active rosettes (compared to controls) was noted for stage IV cases (p less than 0.01) and rose with the stage. The formation of rosettes was reduced in 50 squamous carcinomas compared to 12 anaplastic carcinomas for E rosettes (p less than 0.01) and E active (p less than 0.02). If one compares the actuarial survival curves of 37 patients with E act rosettes greater than or equal to 23% and of 29 with a level of less than 23%, the mean survival for all stages combined was 14.1 months in the first group and 8.2 months in the second group. Associated with an extension of the tumour, the immunological system has a role in determining outcome and lymphocytes forming active E rosettes appear to be the subpopulation most closely correlated with survival.

Adenocarcinoma↗