An acid phosphatase from derepressed cells of the yeast form of Yarrowia lipolyrica was purified 176-fold by ammonium sulfate precipitation, chromatography on DEAE-Sephacel and gel filtration in Biogel A 5-M. The enzyme is a glycoprotein with a sugar content of 60%. The MICHAELIS constant of the enzyme is 5.5 x M for p-nitrophenyl phosphate as substrate; the isoelectric point estimated by electrofocusing is around 4.6 and the optimum pH is 6.2. Phosphatase activity was destroyed by exposure of the enzyme to 40 "C for 30 min or at pH 3 for 30 min. The purified enzyme shows size heterogeneity within a linear concentration gradient of polyacrylamide (4-20%) which indicates an apparent molecular weight in the range of 90,000-200,000 in the presence of sodium dodecyl sulfate. The heterogeneity of the enzyme is due to its carbohydrate content. as can be demonstrated by gel filtration and by treatment with endoglycosidase H. The carbohydrate-depleted protein has a molecular weight of 60,OOO. Aminoacid analysis revealed a high content of aspartic acid, wrine, threonine, glycine and alanine. Antibodies against the protein moiety show cross reactivity with the acid phosphatase of Saccharomyces cerevisiae.
Acid phosphatases (EC 3.1.3.2) have been described in many yeasts (ARNOLD 1981). These enzymes are derepressed upon inorganic phosphate starvation so that organic phosphates, which must first be cleaved from the organic substrates, can be used. Although the existence of yeast alkaline phosphatases has been described (SCHURR and YAGIL 1971, ONISHI et al. 1979), only the acid phosphatases are secreted and these have received the most attention. Purification and physicochemical characterization of acid phosphatases have been performed in Saccharomyces cerevisiae (SCHWEINGRUBER and SCHWEINGRUBER 1982, BAR-BARIC et al. 1984), Schizosaccharomyces pombe (DIBENEDEITO and TELLER 198 l), Cundida albicans (ODDS and HIERHOLZER 1973), Rhodotorula glutinis (TRIMBLE et al. 1981) etc. The best-known acid phosphatases of yeast are those of S. cerevbiue. Intensive studies have been carried out on their carbohydrate content (KOZULIC et al.