The Gram-negative bacterium Azotobacter chroococcum NCIMB 8003 employs a new glycoside hydrolase family 70 4,6-α-glucanotransferase enzyme (GtfD) to synthesize a reuteran like polymer from maltodextrins and starch.
Biochim Biophys Acta
; 1860(6): 1224-36, 2016 Jun.
Article
em En
| MEDLINE
| ID: mdl-26868718
ABSTRACT
BACKGROUND:
Originally the glycoside hydrolase (GH) family 70 only comprised glucansucrases of lactic acid bacteria which synthesize α-glucan polymers from sucrose. Recently we have identified 2 novel subfamilies of GH70 enzymes represented by the Lactobacillus reuteri 121 GtfB and the Exiguobacterium sibiricum 255-15 GtfC enzymes. Both enzymes catalyze the cleavage of (α1â4) linkages in maltodextrin/starch and the synthesis of consecutive (α1â6) linkages. Here we describe a novel GH70 enzyme from the nitrogen-fixing Gram-negative bacterium Azotobacter chroococcum, designated as GtfD.METHODS:
The purified recombinant GtfD enzyme was biochemically characterized using the amylose-staining assay and its products were identified using profiling chromatographic techniques (TLC and HPAEC-PAD). Glucans produced by the GtfD enzyme were analyzed by HPSEC-MALLS-RI, methylation analysis, 1D/2D [1]H/[13]C NMR spectroscopy and enzymatic degradation studies.RESULTS:
The A. chroococcum GtfD is closely related to GtfC enzymes, sharing the same non-permuted domain organization also found in GH13 enzymes and displaying 4,6-α-glucanotransferase activity. However, the GtfD enzyme is unable to synthesize consecutive (α1â6) glucosidic bonds. Instead, it forms a high molecular mass and branched α-glucan with alternating (α1â4) and (α1â6) linkages from amylose/starch, highly similar to the reuteran polymer synthesized by the L. reuteri GtfA glucansucrase from sucrose.CONCLUSIONS:
In view of its origin and specificity, the GtfD enzyme represents a unique evolutionary intermediate between family GH13 (α-amylase) and GH70 (glucansucrase) enzymes. GENERALSIGNIFICANCE:
This study expands the natural repertoire of starch-converting enzymes providing the first characterization of an enzyme that converts starch into a reuteran-like α-glucan polymer, regarded as a health promoting food ingredient.Palavras-chave
Texto completo:
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Polissacarídeos
/
Amido
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Azotobacter
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Sistema da Enzima Desramificadora do Glicogênio
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Glucanos
Idioma:
En
Revista:
Biochim Biophys Acta
Ano de publicação:
2016
Tipo de documento:
Article
País de afiliação:
Holanda