Purification and characterization of a novel thermostable beta-amylase from Clostridium thermosulphurogenes.
An extracellular beta-amylase from Clostridium thermosulphurogenes was purified 811-fold to homogeneity, and its general molecular, physico-chemical and catalytic properties were determined. The native enzyme was a tetramer of 210 kDa composed of a single type subunit; its 20 amino acid N-terminus displayed 45% homology with Bacillus polymyxa beta-amylase. The beta-amylase was enriched in both acidic and hydrophobic amino acids. The pure enzyme displayed an isoelectric point of 5.1 and a pH activity optimum of 5.5. The optimum temperature for beta-amylase activity was 75 degrees C, and enzyme thermostability at 80 degrees C was enhanced by substrate and Ca2+ addition. The beta-amylase hydrolysed amylose to maltose and amylopectin and glycogen to maltose and limit dextrins, and it was inhibited by alpha- and beta-cyclodextrins. The enzyme displayed kcat. and Km values for boiled soluble starch of 400,000 min-1 per mol and 1.68 mg/ml, respectively. The enzyme was antigenically distinct from plant beta-amylases.
Shen
G J
GJ
Michigan Biotechnology Institute, Lansing 48910.
Saha
B C
BC
Lee
Y E
YE
Bhatnagar
L
L
Zeikus
J G
JG
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D000681:Amylases / Q000302:isolation & purification*; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D003013:Clostridium / Q000201:enzymology*; D003505:Cyclodextrins / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation / Q000187:drug effects; D008969:Molecular Sequence Data; D008970:Molecular Weight; D013379:Substrate Specificity; D013696:Temperature; D047391:alpha-Cyclodextrins; D001614:beta-Amylase / Q000037:antagonists & inhibitors / Q000302:isolation & purification* / Q000378:metabolism
D000596:Amino Acids; D003505:Cyclodextrins; D047391:alpha-Cyclodextrins; D000681:Amylases; D001614:beta-Amylase; C032613:alpha-cyclodextrin