Acid phosphatase of potato tubers (Solanum tuberosum L). Purification, properties, sugar and amino acid composition.
Kulcsszavak
Absztrakt
1. Acid phosphatase (AcPase) from potato tubers was purified by tannic acid fractionation, DEAE-cellulose chromatography, filtration on Bio-Gel P-150 and affinity chromatography on Con A-Sepharose. The enzyme was purified 260-fold and was electrophoretically homogeneous; its mol. mass is about 69 000. 2. The carbohydrate component accounts for 16.6% of the total enzyme weight and includes mannose (5.6%), rhamnose (3.4%), glucose (2.5%), galactose (1.5%) and glucosamine (3.6%). In the amino acid composition aspartic acid, glutamic acid, serine and glycine account for 37.7% of total amino acid residues. 3. Optimum pH is at 5.0-5.3. The enzyme activity was reduced by half after 30 min incubation at 60 degrees C, and was fully abolished after 2 h incubation at 70 degrees C. The enzyme is a nonspecific phosphomonoesterase; aromatic phosphomonoesters and inorganic pyrophosphate can serve as substrates. Apparent Km values were 1.25 mM and 40 mM for p-nitrophenylphosphate and inorganic pyrophosphate, respectively. The enzyme is inhibited by MoO42-, Zn2+, Hg2+ and urea. Inhibition caused by urea was reversible at urea concentration below 9 M.