Enzymatic characterisation of Novamyl, a thermostable alpha-amylase
1998
Christophersen, C. | Otzen, D.E. | Norman, B.E. | Christensen, S. | Schaefer, T.
The thermostable alpha-amylase Novamyl is used in the baking industry as an antistaling agent due to its ability to reduce retrogradation of amylopectin. We have studied its enzymatic properties at pH 5.0. We make two main conclusions: (1) Novamyl shows sequence homology to cycloglycosyl transferases (CGTases); like these enzymes, Novamyl cleaves cyclodextrins, forms transglycosylation products and is subject to product inhibition by maltose. Novamyl has 5 subsites in the active site and is also subject to substrate inhibition. (2) Novamyl is clearly different from exoglucanases like beta-amylase and glucoamylase. It is able to hydrolyse a pentasaccharide with bulky substituents at both ends (INdp5) and is inhibited by the alpha-amylase inhibitor Trestatin A. Although Novamyl appears unable to hydrolyse alpha-1,6-linkages, it is able to degrade amylopectin to a greater extent than beta-amylase as well as beta-limit dextrins. Novamyl degrades amylose in such a manner that initially the molecular weight is drastically reduced while beta-amylase does not show any detectable effect on the molecular weight of this substrate. Products of the degradation of amylopectin and amylose by Novamyl are maltose and oligosaccharides, whereas beta-amylase and glucoamylase produce only maltose and glucose, respectively. This was shown in baking experiments as well.
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