Bohn Lisbeth, Josefsen Lone, Meyer Anne S, Rasmussen Søren K
Department of Agricultural Sciences, Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark.
J Agric Food Chem. 2007 Sep 5;55(18):7547-52. doi: 10.1021/jf071191t. Epub 2007 Aug 15.
Wheat phytase was purified to investigate the action of the enzyme toward its pure substrate (phytic acid - myo-inositol hexakisphosphate) and its naturally occurring substrate (phytate globoids). Phytate globoids were purified to homogeneity from wheat bran, and their nutritionally relevant parameters were quantified by ICP-MS. The main components of the globoids were phytic acid (40% w/w), protein (46% w/w), and several minerals, in particular, K > Mg > Ca > Fe (in concentration order). Investigation of enzyme kinetics revealed that K(m) and V(max) decreased by 29 and 37%, respectively, when pure phytic acid was replaced with phytate globoids as substrate. Time course degradation of phytic acid or phytate globoids using purified wheat phytase was followed by HPIC identification of inositol phosphates appearing and disappearing as products. In both cases, enzymatic degradation initiated at both the 3- and 6-positions of phytic acid and end products were inositol and phosphate.
对小麦植酸酶进行纯化，以研究该酶对其纯底物（植酸 - 肌醇六磷酸）及其天然存在的底物（植酸球状体）的作用。从麦麸中将植酸球状体纯化至同质，并通过电感耦合等离子体质谱法对其营养相关参数进行定量。植酸球状体的主要成分是植酸（40% w/w）、蛋白质（46% w/w）和几种矿物质，特别是K > Mg > Ca > Fe（按浓度顺序）。酶动力学研究表明，当以植酸球状体替代纯植酸作为底物时，米氏常数（Km）和最大反应速度（Vmax）分别降低了29%和37%。使用纯化的小麦植酸酶对植酸或植酸球状体进行时间进程降解，随后通过高效离子交换色谱法鉴定作为产物出现和消失的肌醇磷酸。在这两种情况下，酶促降解均从植酸的3位和6位开始，最终产物为肌醇和磷酸盐。
