Purification and Characterization of Phospholipase B from Kluyveromyces lactis, and Cloning of Phospholipase B gene

概要

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Phospholipase B (PLB) from the yeast Kluyveromyces lactis was purified to homogeneity from culture medium. The enzyme was highly glycosylated with apparent molecular mass of 160-250kDa, and had two pH optima, at pH 2.0 and pH 7.5. At acidic pH the enzyme hydrolyzed all phospholipid substrates tested here without metal ion. On the other hand, at alkaline pH the enzyme showed substrate specificity for phosphatidylcholine and lysophosphatidylcholine and required Ca^<2+>, Fe^<3+>, or Al^<3+> for the activity. The alkaline activity was increased more than 20-fold in the presence of Al^<3+> compared to that in the presence of Ca^<2+>. cDNA sequence of PLB (KlPLB) was analyzed by a combination of several PCR procedures. KlPLB encoded a protein consist of 640 amino acids and the deduced amino acid sequence showed 66.7% similarity with the T. delbrueckii PLB. The amino acid sequence contained the lipase consensus sequence (G-X-S-X-G) and the catalytic aspartic acid motif. Replacement of Arg-112 or Asp-406 with alanine caused loss of the enzymatic actiivity at both pH. These results suggested that PLB activity are dependent on a catalytic mechanism similar to that of cytosolic phospholipase A_2.
社団法人日本農芸化学会の論文
1999-01-23