Biomedical subjects

Olivier Berteau

Publications and source records attributed to Olivier Berteau.

9 recordsLinked to original sources

PubMed2006

Dinucleotide spore photoproduct, a minimal substrate of the DNA repair spore photoproduct lyase enzyme from Bacillus subtilis.

The overwhelming majority of DNA photoproducts in UV-irradiated spores is a unique thymine dimer called spore photoproduct (SP, 5-thymine-5,6-dihydrothymine). This lesion is repaired by the spore photoproduct lyase (SP lyase) enzyme that directly reverts SP to two unmodified thymines. The SP lyase is an S-adenosylmethionine-dependent iron-sulfur protein that belongs to the radical S-adenosylmethionine superfamily. In this study, by using a well characterized preparation of the SP lyase enzyme from Bacillus subtilis, we show that SP in the form of a dinucleoside monophosphate (spore photoproduct of thymidilyl-(3'-5')-thymidine) is efficiently repaired, allowing a kinetic characterization of the enzyme. The preparation of this new substrate is described, and its identity is confirmed by mass spectrometry and comparison with authentic spore photoproduct. The fact that the spore photoproduct of thymidilyl-(3'-5')-thymidine dimer is repaired by SP lyase may indicate that the SP lesion does not absolutely need to be contained within a single- or double-stranded DNA for recognition and repaired by the SP lyase enzyme.

Bacillus subtilis↗

PubMed2006

A new type of bacterial sulfatase reveals a novel maturation pathway in prokaryotes.

Sulfatases are a highly conserved family of enzymes found in all three domains of life. To be active, sulfatases undergo a unique post-translational modification leading to the conversion of either a critical cysteine ("Cys-type" sulfatases) or a serine ("Ser-type" sulfatases) into a Calpha-formylglycine (FGly). This conversion depends on a strictly conserved sequence called "sulfatase signature" (C/S)XPXR. In a search for new enzymes from the human microbiota, we identified the first sulfatase from Firmicutes. Matrix-assisted laser desorption ionization time-of-flight analysis revealed that this enzyme undergoes conversion of its critical cysteine residue into FGly, even though it has a modified (C/S)XAXR sulfatase signature. Examination of the bacterial and archaeal genomes sequenced to date has identified many genes bearing this new motif, suggesting that the definition of the sulfatase signature should be expanded. Furthermore, we have also identified a new Cys-type sulfatase-maturating enzyme that catalyzes the conversion of cysteine into FGly, in anaerobic conditions, whereas the only enzyme reported so far to be able to catalyze this reaction is oxygen-dependent. The new enzyme belongs to the radical S-adenosyl-l-methionine enzyme superfamily and is related to the Ser-type sulfatase-maturating enzymes. This finding leads to the definition of a new enzyme family of sulfatase-maturating enzymes that we have named anSME (anaerobic sulfatase-maturating enzyme). This family includes enzymes able to maturate Cys-type as well as Ser-type sulfatases in anaerobic conditions. In conclusion, our results lead to a new scheme for the biochemistry of sulfatases maturation and suggest that the number of genes and bacterial species encoding sulfatase enzymes is currently underestimated.

Amino Acid Motifs↗

PubMed2006

The spore photoproduct lyase repairs the 5S- and not the 5R-configured spore photoproduct DNA lesion.

The spore photoproduct lyase is a Fe-S/AdoMet DNA repair enzyme, which directly repairs spore lesions, induced by UV irradiation of spores, using an unknown radical mechanism. The air sensitive radical SAM enzyme was for the first time challenged with synthetically pure substrates. It was found that the enzyme recognizes a synthetic 5S-configured spore lesion without the central phosphodiester bond. The 5R-configured lesion is in contrast to current belief not a substrate.

Bacillus subtilis↗

PubMed2004

Atomic mapping of the interactions between the antiviral agent cyanovirin-N and oligomannosides by saturation-transfer difference NMR.

The minimum oligosaccharide structure required for binding to the potent HIV-inactivating protein cyanovirin-N (CV-N) was determined by saturation-transfer difference (STD) NMR spectroscopy. Despite the low molecular mass of the protein (11 kDa), STD-NMR spectroscopy allowed the precise atomic mapping of the interactions between CV-N and various di- and trimannosides, substructures of Man-9, the predominant oligosaccharide on the HIV viral surface glycoprotein gp120. Contacts with mannosides containing the terminal Manalpha(1-->2)Manalpha unit of Man-9 were observed, while (1-->3)- and (1-6)-linked di- and trimannosides showed no interactions, demonstrating that the terminal Manalpha(1-->2)Manalpha structure plays a key role in the interaction. Precise epitope mapping revealed that, for Manalpha(1-->2)ManalphaOMe, Manalpha(1-->2)Manalpha(1-->3)ManalphaOMe, and Manalpha(1-->2)Manalpha(1-->6)ManalphaOMe, the protein is in close contact with H2, H3, and H4 of the nonreducing terminal mannose unit. In contrast, the STD-NMR spectrum of the CV-N/trisaccharide Manalpha(1-->2)Manalpha(1-->2)ManalphaOMe complex was markedly different, with resonances on all sugar units displaying equal enhancements, suggesting that CV-N is able to discriminate between the three structurally related trisaccharides.

Anti-HIV Agents↗

PubMed2004

Alpha-L-fucosidases: exoglycosidases with unusual transglycosylation properties.

Apha-LFucosidases (EC 3.2.1.51), the only members of the CAZy family GH-29, are widespread glycosidases involved in many biological processes including inflammation, metastasis, and the lysosomal storage disease fucosidosis. Despite their biological significance, information concerning the mechanism of alpha-Lfucosidases has only recently become available. In an attempt to obtain further data concerning their mechanism, we have investigated the hydrolytic and transglycosylation properties of a canine and a mollusk (Pecten maximus) alpha-Lfucosidase. Our results show that, despite the evolutionary distance between these two species, both enzymes have similar hydrolysis and transglycosylation properties. Surprisingly, we found that, starting from monosaccharides, these exoglycosidases were able to catalyze efficiently the synthesis of highly branched fuco-oligosaccharides as large as tetrasaccharides, a unique feature for a wild-type exoglycosidase. The structural analysis of the compounds formed revealed that the regioselectivity of alpha-Lfucosidases is strongly influenced by the structure of the acceptor. This leads us to propose an enzymatic approach for the preparative synthesis of fuco-oligosaccharides. This will not only allow the synthesis of biological determinants containing fucose but also of new fucose-containing oligosaccharides as alpha-glycosynthases appear to be difficult to obtain.

Animals↗

PubMed2004

Web resources for the carbohydrate chemist.

Bioinformatics has played a pivotal role in advancing genetics and protein sciences. The large amount of information generated by genomics, and now proteomics, has been a driving force. By comparison, glycobiology still generates small amounts of data. The need to organize our knowledge about carbohydrates is however growing constantly and has given rise to an increasing number of public databases and freely available tools. This review gives an overview of the carbohydrate-oriented resources currently available on the Internet. Many of the resources are seldom referred to in the literature and difficult to find, in part because of the constant flux of the net itself, but also because many efforts have been lead by a single individual. As the World Wide Web has matured the number of 'permanent' resources, maintained by organizations rather than individuals, has increased. In this paper, we present some of the more useful and accessible public tools and databases. There are also a few commercial initiatives but these have not been reviewed.

Biochemical Phenomena↗

PubMed2003

Glycosidase-substrate interactions analysis by STD-NMR spectroscopy: study of alpha-L-fucosidase.

Saturation transfer difference-nuclear magnetic resonance (STD-NMR) is a recently developed method used to study the interaction between large proteins and small ligands. It has been successfully employed for various interactions including those between oligosaccharides or glycomimetics, and binding proteins such as lectins and antibodies. We have demonstrated that this method can be used to directly study the interaction between glycosidases and their substrates. We chose to study alpha-l-fucosidases, which, despite their wide distribution among living organisms and their biological significance, have not been studied with regard to their reaction mechanism. We were able for the first time to show direct evidences for the minimum structural requirements for a compound to interact with these enzymes. These findings will be useful for the design of new inhibitors and to optimize the synthetic properties (transglycosylation) of alpha-l-fucosidases.

1-Deoxynojirimycin↗

PubMed2003

Sulfated fucans, fresh perspectives: structures, functions, and biological properties of sulfated fucans and an overview of enzymes active toward this class of polysaccharide.

Sulfated fucans, frequently referred to simply as fucans, constitute a class of polysaccharides first isolated in 1913. For many years fucans were regarded only as a potential source of l-fucose, although their anticoagulant activity was known. Even as the potent effects of fucans on physiological systems have become better characterized, structural studies have lagged behind. Recently the search for new drugs has raised increased interest in sulfated fucans. In the past few years, several structures of algal and invertebrate fucans have been solved, and many aspects of their biological activity have been elucidated. From this work emerges a more interesting picture of this class of polysaccharides than was previously suspected. The availability of purified fucans and fucan fractions with simple, but varied structures, in conjunction with the development of new enzymatic tools, demonstrate that the biological properties of sulfated fucans are not only a simple function of their charge density but also are determined by detailed structural features.

Animals↗

PubMed2002

Characterization of a new alpha-L-fucosidase isolated from the marine mollusk Pecten maximus that catalyzes the hydrolysis of alpha-L-fucose from algal fucoidan (Ascophyllum nodosum).

Algal fucoidan is an alpha-L-fucose-based polysaccharide endowed with important biological properties for which the structure has not yet been fully elucidated. In an attempt to implement new enzymatic tools for structural study of this polysaccharide, we have found a fucosidase activity in the digestive glands of the common marine mollusk Pecten maximus, which is active on a fucoidan extracted from the brown algae Ascophyllum nodosum. We now report the purification and characterization of this alpha-L-fucosidase (EC 3.2.1.51). The enzyme was purified by three chromatographic steps, including an essential affinity chromatography based on the glycosidase inhibitor analog 6-amino-deoxymannojirimycin as the ligand. The purified alpha-L-fucosidase is a tetrameric glycoprotein of 200 kDa that hydrolyzes the synthetic substrate p-nitrophenyl alpha-L-fucopyranoside with a K(m) value of 650 microM. This enzyme has high catalytic activity (85 micromol x min(-1) x mg(-1)) compared with the other known fucosidases and also possesses an unusual thermal stability. The purified alpha-L-fucosidase is a retaining glycosidase. The activity of the purified fucosidase was determined on two structurally different fucoidans of the brown algae A. nodosum and Fucus vesiculosus to delineate glycosidic bond specificity. This report is to our knowledge the first demonstration of a fucosidase that can efficiently release alpha-L-fucose from fucoidan.

Animals↗