A single gene directs synthesis of a precursor protein with beta- and alpha-amylase activities in Bacillus polymyxa.
The Bacillus polymyxa amylase gene comprises 3,588 nucleotides. The mature amylase comprises 1,161 amino acids with a molecular weight of 127,314. The gene appeared to be divided into two portions by the direct-repeat sequence located at almost the middle of the gene. The 5' region upstream of the direct-repeat sequence was shown to be responsible for the synthesis of beta-amylase. The 3' region downstream of the direct-repeat sequence contained four sequences homologous with those in other alpha-amylases, such as Taka-amylase A. The 48-kilodalton (kDa) amylase isolated from B. polymyxa was proven to have alpha-amylase activity. The amino acid sequences of the peptides generated from the 48-kDa amylase showed complete agreement with the predicted amino acid sequence of the C-terminal portion. The B. polymyxa amylase gene was therefore concluded to contain in-phase beta- and alpha-amylase-coding sequences in the 5' and 3' regions, respectively. A precursor protein, a 130-kDa amylase, directed by a plasmid, pYN520, carrying the entire amylase gene, had both beta- and alpha-amylase activities. This represents the first report of a single protein precursor in procaryotes that gives rise to two enzymes.
Uozumi
N
N
Department of Food Science and Technology, Faculty of Agriculture, Nagoya University, Japan.
Sakurai
K
K
Sasaki
T
T
Takekawa
S
S
Yamagata
H
H
Tsukagoshi
N
N
Udaka
S
S
D000595:Amino Acid Sequence; D000681:Amylases / Q000235:genetics*; D001407:Bacillus / Q000201:enzymology / Q000235:genetics*; D001483:Base Sequence; D004792:Enzyme Precursors / Q000235:genetics* / Q000302:isolation & purification; D005796:Genes; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D010957:Plasmids; D000516:alpha-Amylases / Q000235:genetics*; D001614:beta-Amylase / Q000235:genetics*
D004792:Enzyme Precursors; D000681:Amylases; D000516:alpha-Amylases; D001614:beta-Amylase