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Phylogenetic and biochemical characterization of a novel cluster of intracellular fungal α-amylase enzymes

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Author: Kaaij, R.M. van der · Janeček, Š. · Maarel, M.J.E.C. van der · Dijkhuizen, L.
Institution: TNO Kwaliteit van Leven
Source:Microbiology, 12, 153, 4003-4015
Identifier: 240324
doi: doi:10.1099/mic.0.2007/008607-0
Keywords: Nutrition · Food technology · amylase · amylase 1p · amylase D · glucan · maltotriose · starch · article · Ascomycetes · Aspergillus niger · Basidiomycetes · enzyme activity · enzyme analysis · gene cluster · gene overexpression · gene sequence · Histoplasma capsulatum · nonhuman · nucleotide sequence · phylogeny · priority journal · protein purification · sequence homology · alpha-Amylase · Amino Acid Sequence · Animals · Aspergillus niger · Cell Wall · Fungal Proteins · Fungi · Glucans · Histoplasma · Molecular Sequence Data · Phylogeny · Sequence Alignment · Starch · Substrate Specificity · Ajellomyces capsulatus · Ascomycota · Aspergillus niger · Basidiomycota · Fungi


Currently known fungal α-amylases are well-characterized extracellular enzymes that are classified into glycoside hydrolase subfamily GH13_1. This study describes the identification, and phylogenetic and biochemical analysis of novel intracellular fungal α-amylases. The phylogenetic analysis shows that they cluster in the recently identified subfamily GH135_5 and display very low similarity to fungal α-amylases of family GH13_1. Homologues of these intracellular enzymes are present in the genome sequences of all filamentous fungi studied, including ascomycetes and basidiomycetes. One of the enzymes belonging to this new group, Amy1p from Histoplasma capsulatum, has recently been functionally linked to the formation of cell wall α-glucan. To study the biochemical characteristics of this novel cluster of α-amylases, we overexpressed and purified a homologue from Aspergillus niger, AmyD, and studied its activity product profile with starch and related substrates. AmyD has a relatively low hydrolysing activity on starch (2.2 U mg-1), producing mainly maltotriose. A possible function of these enzymes in relation to cell wall α-glucan synthesis is discussed. © 2007 SGM.