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C Duez

Publications and source records attributed to C Duez.

63 records · Page 4Linked to original sources
PubMed1981

The penicillin-binding site in the exocellular DD-carboxypeptidase-transpeptidase of Actinomadura R39.

Heat denaturation and Pronase degradation of the complex previously formed between benzylpenicillin and the exocellular DD-carboxypeptidase-transpeptidase of Actinomadura R39 yields a heptapeptide H-Leu-Pro-Ala-Ser-Asn-Gly-Val-OH, where the benzylpenicilloyl group is ester-linked to the serine residue. This linkage is very labile and its hydrolysis causes the release of benzylpenicilloate. In contrast, the native benzylpenicilloyl-enzyme complex is very stable (half-life 70 h at 37 degrees C) and its breakdown proceeds via fragmentation of the bound benzylpenicilloyl group [Fuad, Frère, Ghuysen, Duez & Iwatsubo (1976) Biochem. J. 155, 623-629].

Amino Acid Sequence↗
PubMed1978

The exocellular DD-carboxypeptidase-endopeptidase from Streptomyces albus G. Purification and chemical properties.

The exocellular DD-carboxypeptidase-endopeptidase of Streptomyces albus G was purified to protein homogeneity and compared with the exocellular DD-carboxypeptidases-transpeptidases of Streptomyces R61 and Actinomadura R39. The S. albus G enzyme, as it is isolated, occurs in two forms. Enzyme I (30% of the total amount) and enzyme II (70% of the total amount) are identical in all respects, except that, by polyacrylamide-gel electrophoresis in the presence of sodium dodecyl sulphate, enzyme I has an apparent mol. wt. (9000) that is half of that found by molecular-sieve filtration under non-denaturing conditions. Irrespective of the technique used, enzyme II has an apparent mol. wt. of about 18500.

Alanine↗
PubMed1976

Mode of interaction between beta-lactam antibiotics and the exocellular DD-carboxypeptidase--transpeptidase from Streptomyces R39.

The exocellular DD-carboxypeptidase-transpeptidase of Streptomyces R39 is inhibited by beta-lactam antibiotics according to the same general scheme of reaction as the exocellular DD-carboxypeptidase-transpeptidase of Streptomyces R61. However, the values for the kinetic constants involved in the reaction are very different for the two enzymes and provide an explanation for the observation that the R39 enzyme is more sensitive to beta-lactam antibiotics than the R61 enzyme. Further, particular beta-lactams influence the kinetic constants to different extents depending on the source of the enzyme, so that a physical basis for the spectrum of antibiotic activity against particular enzyme systems is provided.

Carboxypeptidases↗
PubMedDate not supplied

Human IgE in severe combined immunodeficiency mice reconstituted with peripheral blood mononuclear cells from Dermatophagoides pteronyssinus-sensitive patients.

We studied conditions of human IgE formation in severe combined immunodeficiency (SCID) mice engrafted with peripheral blood mononuclear cells (PBMCs) from allergic patients sensitive to Dermatophagoides pteronyssinus (D.pt.). With 10 x 10(6) PBMCs injected intraperitoneally, the hu-SCID mice developed an IgE response, but only if experimental animals were immunized with the related allergen. Two routes of immunization were tested: intraperitoneal and inhalation. In these experimental conditions (allergen given at day 14 after reconstitution), a significant rise in total serum IgE but also in specific anti-D.pt. IgE was observed. No human IgE could be detected within 3-4 weeks after immunization with an unrelated allergen. Similarly, when mice were engrafted with PBMCs from nonallergic donors, even after D.pt. administration, no significant increase of serum IgE was detectable, while an IgG response was regularly found. Thus SCID mice could represent a useful model to analyze IgE production as well as the conditions of immunization required to obtain an optimal response.

Administration, Inhalation↗
PubMedDate not supplied

Modulation of the allergen-induced human IgE response in Hu-SCID mice: inhibitory effect of human recombinant IFN-gamma and allergen-derived lipopeptide.

We have previously established a model to study the in vivo human IgE response using humanized SCID mice. Allergic SCID mice were obtained following intraperitoneal injection with mononuclear cells from Dermatophagoides pteronyssinus (Dpt)-sensitive patients, and sensitization by Dpt allergen intraperitoneal injection (immunization) or Dpt aerosol (inhalation). Human serum IgE was measured in allergic SCID mice after administration of human recombinant IFN-gamma or the lipopeptide LP 52-71 (derived from peptide p52-71 from Der p 1, Dpt major allergen, coupled to a lipophilic moiety), during the immunization or the inhalation phase. IFN-gamma inhibited human IgE production when given at the time of immunization, but not during inhalation. This effect was long-lasting as Dpt aerosol, given one month after immunization and IFN-gamma administration, failed to increase IgE levels. Unlike Dpt or p52-71, LP 52-71 failed to induce human IgE production at day 14 and 21 after its injection, but did inhibit the development of the IgE response after a secondary Dpt-challenge. Moreover, LP 52-71 administration 14 days after Dpt inhalation decreased IgE levels, in contrast to peptide 52-71, which increased IgE levels. Thus, taken together these results indicate that the development of the human IgE response in allergic SCID mice can be modulated by modified allergen and a Th1 cytokine.

Animals↗