title: Purification and characterization of banana fruit acid phosphatase.
abstract: An acid phosphatase (APase, EC 3.1.3.2) from ripened banana (Musa cavendishii L. cv. Cavendish) fruit has been purified 1,876-fold to electrophoretic homogeneity and a final p-nitrophenylphosphate (pNPP)-hydrolyzing specific activity of 745 micromol Pi produced (mg protein)(-1) min(-1). Non-denaturing PAGE of the final preparation resolved a single protein-staining band that co-migrated with APase activity. SDS-PAGE and analytical gel filtration demonstrated that the purified enzyme exists as a 40-kDa monomer. That the enzyme is glycosylated was indicated by its tight absorption to Concanavalin A-Sepharose. Banana APase was relatively heat stable, displayed a symmetrical pH/activity profile with maximal activity at pH 5.8, and was activated 180% and 150% by 5 mM Mn2+ and Mg2+, respectively. The enzyme exhibited a broad substrate selectivity, with maximal specificity constants (Vmax/Km) obtained with pNPP, phosphoenolpyruvate, phenyl phosphate, and O-phospho-L-tyrosine. Potent inhibition by Pi, molybdate, vanadate, arsenate, and Zn2+ was observed. Putative metabolic functions of the APase are discussed in relation to maintaining significant Pi mobility during banana fruit ripening.
authors.affiliation: Department of Biology, Queen's University, Kingston, Ontario, Canada.
authors.forename: W L
authors.initials: WL
authors.lastname: Turner
authors.forename: W C
authors.initials: WC
authors.lastname: Plaxton
mesh_terms: D000135:Acid Phosphatase / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism; D002118:Calcium / Q000494:pharmacology; D002413:Cations, Divalent / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D005638:Fruit / Q000201:enzymology* / Q000254:growth & development; D006031:Glycosylation; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D008345:Manganese / Q000494:pharmacology; D028521:Musa / Q000201:enzymology* / Q000254:growth & development; D010710:Phosphates / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D002413:Cations, Divalent; D010710:Phosphates; D008345:Manganese; D000135:Acid Phosphatase; D008274:Magnesium; D002118:Calcium