PMID:1628664

Citation	Liebl, W, Feil, R, Gabelsberger, J, Kellermann, J and Schleifer, KH (1992) Purification and characterization of a novel thermostable 4-alpha-glucanotransferase of Thermotoga maritima cloned in Escherichia coli. Eur. J. Biochem. 207:81-8
Abstract	Maltodextrin glycosyltransferase (4-alpha-glucanotransferase) of the extremely thermophilic ancestral bacterium Thermotoga maritima has been purified from an Escherichia coli clone expressing the corresponding T. maritima MSB8 chromosomal gene. T. maritima 4-alpha-glucanotransferase, an approximately 53-kDa monomeric enzyme, is the most thermophilic glycosyltransferase described to date. It retained more than 90% of its maximum activity at temperatures from 55 degrees C up to 80 degrees C. The proposed action modus is the transfer of 1,4-alpha-glucanosyl chains, thus resulting in the disproportionation of 1,4-alpha-glucans. It converted soluble starch, amylopectin, and amylose, thereby changing the iodine staining properties of these substrates. The addition of low-molecular-mass malto-oligosaccharides, which act as glucanosyl acceptor molecules, enhanced the reaction and resulted in the formation of a series of linear maltohomologues from two to more than nine glucose units in size. Use of either of the malto-oligosaccharides maltotetraose, maltopentaose, maltohexaose, or maltoheptaose as sole substrate also yielded linear maltohomologues. On the other hand, maltose and maltotriose were not disproportionated by 4-alpha-glucanotransferase, although both were good acceptors for glucanosyl transfer. Glucose did not function as an acceptor in transfer reactions. Glucose also never appeared as a reaction product. The chain length of glucanosyl segments transferred ranged from two to probably far more than six glucose residues. Comparison of the N-terminal amino acid sequence of 4-alpha-glucanotransferase with other published protein sequences revealed significant similarity to sequences near the N-termini of various eucaryotic maltases and bacterial cyclodextrin glycosyltransferases, suggesting its relatedness on the molecular level with other starch- and maltodextrin-converting enzymes.
Links	PubMed
Keywords	Amino Acid Sequence; Base Sequence; Carbohydrates/analysis; Chromatography, Gel; Chromatography, Ion Exchange; Enzyme Stability; Escherichia coli/genetics; Glycogen Debranching Enzyme System/genetics; Glycogen Debranching Enzyme System/isolation & purification; Glycogen Debranching Enzyme System/metabolism; Gram-Negative Anaerobic Bacteria/enzymology; Gram-Negative Anaerobic Bacteria/genetics; Hot Temperature; Kinetics; Molecular Sequence Data; Oligosaccharides/pharmacology; Recombinant Proteins/isolation & purification; Recombinant Proteins/metabolism; Thermodynamics
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
THEMA:MGTA		GO:0004134: 4-alpha-glucanotransferase activity	ECO:0000314:		F		Fig 6, other data discussed but not shown	complete
THEMA:MGTA		GO:0009313: oligosaccharide catabolic process	ECO:0000314:		P		Table 2	complete

References

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