Discovery and Characterization of a Phosphatidic Acid-hydrolyzing Phosphatase from <i>Streptomyces mirabilis</i>, and its Use for Phospholipid Refinement

An acid phosphatase gene from Streptomyces mirabilis NBRC13450 was cloned and expressed in a recombinant strain of Streptomyces lividans TK24. The recombinant enzyme, named SmACP, was secreted into the culture medium, and subsequently purified to homogeneity. The purified SmACP exhibited an optimal pH range of 5.5-6.5 for hydrolyzing p-nitrophenyl phosphate. Its activity remained unaffected by Ca²⁺, Mg²⁺, Zn²⁺, and EDTA. Notably, SmACP was capable of hydrolyzing a variety of phosphomonoesters, including long-chain phosphatidic acid (PA) and lyso-PA, in addition to other water-soluble monoesters. However, it showed no activity toward phosphodiester-type phospholipids, such as phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylinositol and phosphatidylserine. This substrate specificity highlights SmACP's potential for selectively removing PA from phospholipid mixtures, which could be valuable in industrial phospholipid production. This is the first report on the identification of a secreted PA-degrading phosphatase, including its DNA and amino acid sequences.