A unique beta-agarase, AgaA, from a marine bacterium, Vibrio sp. strain PO-303.
The agaA gene encoding beta-agarase-a (AgaA) was cloned from the chromosomal DNA of a marine bacterium, Vibrio sp. strain PO-303. The nucleotide sequence of the agaA gene consists of 2,958 bp and encodes a protein of 985 amino acids with a molecular mass of 106,062 Da. The deduced enzyme protein contains a typical N-terminal signal peptide of 29 amino acid residues, followed by a 266 amino acid sequence that is homologous to catalytic module of family 16 glycoside hydrolases, a bacterial immunoglobulin group 2 (Big-2)-like domain of 52 amino acid residues, two carbohydrate-binding modules of family 6 separated from Big-2-like domain by nine times repeated GDDTDP amino acid sequence. AgaA is the first agarase that was identified to possess a Big-2-like domain. The recombinant AgaA (rAgaA) expressed in Escherichia coli exhibited maximal activity around 40 degrees C and pH 7.5, with a specific activity of 16.4 units mg(-1), a K (m) of 1.10 mg ml(-1), and a V (max) of 22.5 micromol min(-1) mg(-1) for agarose. The rAgaA hydrolyzed neoagarohexaose, but did not act on neoagarotetraose and neoagarobiose.
Dong
Jinhua
J
Graduate School of Bioresources, Mie University, 1577 Kurimamachiya, Tsu, Mie 514-8507, Japan.
Tamaru
Yutaka
Y
Araki
Toshiyoshi
T
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D003001:Cloning, Molecular; D004591:Electrophoresis, Polyacrylamide Gel; D015964:Gene Expression Regulation, Bacterial; D015971:Gene Expression Regulation, Enzymologic; D006026:Glycoside Hydrolases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014733:Vibrio / Q000201:enzymology* / Q000235:genetics
D001426:Bacterial Proteins; D011994:Recombinant Proteins; D006026:Glycoside Hydrolases; C019624:agarase