Biochemical and structural characterization of the complex agarolytic enzyme system from the marine bacterium Zobellia galactanivorans.
J Biol Chem
; 287(36): 30571-84, 2012 Aug 31.
Article
em En
| MEDLINE
| ID: mdl-22778272
ABSTRACT
Zobellia galactanivorans is an emerging model bacterium for the bioconversion of algal biomass. Notably, this marine Bacteroidetes possesses a complex agarolytic system comprising four ß-agarases and five ß-porphyranases, all belonging to the glycoside hydrolase family 16. Although ß-agarases are specific for the neutral agarobiose moieties, the recently discovered ß-porphyranases degrade the sulfated polymers found in various quantities in natural agars. Here, we report the biochemical and structural comparison of five ß-porphyranases and ß-agarases from Z. galactanivorans. The respective degradation patterns of two ß-porphyranases and three ß-agarases are analyzed by their action on defined hybrid oligosaccharides. In light of the high resolution crystal structures, the biochemical results allowed a detailed mapping of substrate specificities along the active site groove of the enzymes. Although PorA displays a strict requirement for C6-sulfate in the -2- and +1-binding subsites, PorB tolerates the presence of 3-6-anhydro-l-galactose in subsite -2. Both enzymes do not accept methylation of the galactose unit in the -1 subsite. The ß-agarase AgaD requires at least four consecutive agarose units (DP8) and is highly intolerant to modifications, whereas for AgaB oligosaccharides containing C6-sulfate groups at the -4, +1, and +3 positions are still degraded. Together with a transcriptional analysis of the expression of these enzymes, the structural and biochemical results allow proposition of a model scheme for the agarolytic system of Z. galactanivorans.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Proteínas de Bactérias
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Modelos Moleculares
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Ágar
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Flavobacteriaceae
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Glicosídeo Hidrolases
Idioma:
En
Ano de publicação:
2012
Tipo de documento:
Article