title: The hydrodynamic properties and kinetic constants with natural substrates of the esterase from Malus pumila fruit.
abstract: 1. An esterase (EC 3.1.1.1) from Malus pumila fruit was purified to homogeneity using ammonium sulphate precipitation, absorption on hydroxyapatite, dye Matrex affinity chromatography, S.300 Sephacryl chromatography and wide-range isoelectric focusing. 2. Kinetic constants of these preparations were established for a series of natural ester substrates. Greatest apparent affinity was for acetate esters containing seven or eight-carbon skeletons and least for four-carbon skeletons. 3. The purified protein gave a relative molecular mass of 195000. The enzyme appears to be a tetramer of similar sub-units each with a relative molecular mass of 50000 4. Isoelectric focusing gave a single peak of activity with pI 9.33-9.66. 5. Specific activity increased considerably from small immature fruits to large fruit at the climacteric.
mesh_terms: D004591:Electrophoresis, Polyacrylamide Gel; D004950:Esterases / Q000302:isolation & purification* / Q000378:metabolism; D005638:Fruit / Q000032:analysis*; D007525:Isoelectric Focusing; D007700:Kinetics; D013379:Substrate Specificity
chemical_list: D004950:Esterases