期刊
BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS
卷 1774, 期 5, 页码 661-669出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.bbapap.2007.03.010
关键词
Thermoplasma volcanium; maltogenic amylase; thermostability; oligomeric state; subsite structure
Maltogenic amylases (MAases), a subclass of cyclodextrin (CD)-hydrolyzing enzymes belonging to glycoside hydrolase family 13, have been studied extensively, but their physiological roles in microbes and evolutionary relationships with other amylolytic enzymes remain unclear. Here, we report the biochemical properties of a thermostable archaeal MAase from Thermoplasma volcanium GSS 1 (TpMA) for the first time. The primary structure and catalytic properties of TpMA were similar to those of MAases, such as possession of an extra domain at its N-terminal and preference for CD over starch. TpMA showed high thermostability and optimal activity at 75 degrees C and 80 degrees C for beta-CD and soluble starch, respectively. The recombinant TpMA exists as a high oligomer in a solution and the oligomeric TpMA was dissociated into dimer and monomer mixture by a high concentration of NaCl. The substrate preference and then-no stability of TpMA were significantly dependent on the oligomeric state of the enzyme. However, TpMA exhibited distinguishable characteristics from those of bacterial MAases. The transglycosylation pattern of TpMA was opposite to that of bacterial MAases. TpMA formed more alpha-1,4-glycosidic linked transfer product than alpha-1,6-linked products. Like as a-amylases, notably, TpMA has a longer subsite structure than those of other CD-degrading enzymes. Our findings in this study suggest that TpMA, the archaeal MAase, shares characteristics of both bacterial MAases and a-amylases, and locates in the middle of the evolutionary process between alpha-amylases and bacterial MAases. (C) 2007 Elsevier B.V. All rights reserved.
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