Phytate-degrading enzymes: regulation of synthesis in microorganisms and plants.

Abstract

Phytate-degrading enzymes, also known as phytases, have a wide distribution in plants, microorganisms and some animal tissues (Konietzny and Greiner, 2002; see Hill and Richardson, Chapter 5, and Mullaney and Ullah, Chapter 7, this volume). They belong to a special class of phosphomonoesterases termed myo-inositol hexakisphosphate phosphohydolases, which are capable of initiating the stepwise release of phosphate residues from phytate (salts of myo-inositol hexakisphosphate), the major storage form of phosphate in plant seeds and pollen. The ability of such enzymes to hydrolyse phytate is usually known only from in vitro assays, and information on their in vivo function is rather limited. As enzymes are classified in general by their in vivo function, the term 'phytate-degrading enzyme' is preferred here to the term 'phytase', and is used throughout the chapter. The classification of enzymes as phytases based solely on in vitro assays becomes problematic when considering enzymes such as glucose-1-phosphatase in Escherichia coli and Enterobacter cloacae. This enzyme can hydrolyse phytate, albeit slowly, in vitro even though this is clearly not its in vivo function. Unless otherwise stated, designation of an enzyme as 'phytatedegrading' is based on in vitro assay using soluble sodium phytate.

Identification of inositol hexakisphosphate binding sites in soils by selective extraction and solution 31P NMR spectroscopy

“…Hence, it is likely that oxalate extractable IP 6 is potentially bioavailable, but utilization will require desorption/dissolution and enzymatic hydrolysis (Giles et al, 2012;Hayes et al, 2000). As this is costly for plants and microbes, degradation of IP 6 in high P fixing soils has been suggested primarily to take place under P or carbon limitation (Greiner, 2007), which might explain the accumulation of high concentrations of IP 6 in temperate soils rich in P and Al/Fe (Celi and Barberis, 2007;Turner, 2007). Even less is known about the stabilization of organic bound IP 6 , but the fate of this IP 6 pool is probably controlled by the same factors that control organic matter dynamics.…”

“…Degradation of IP 6 is catalyzed by phytases which are produced by some plants and many microorganisms (Greiner, 2007;Hill and Richardson, 2007;Richardson, 2007). Several plants, especially transgenic plants, are able to grow on IP 6 as their sole P source in low P sorbing media, but in high P fixing media the growth ceases due to the inaccessibility of strongly-fixed IP 6 for enzymatic degradation (Richardson, 2007).…”

Microbial Phytases and Phytate: Exploring Opportunities for Sustainable Phosphorus Management in Agriculture

“…The enzymes phytases belong to the general class of phosphatases (EC 3.1.3) and hydrolyze phytate to release inorganic phosphorus [47]. Phytases are classified into several families with important differences in structure, substrate specificity, pH-optimum and mechanism of hydrolysis.…”

Phytate Degradation by Different Phosphohydrolase Enzymes: Contrasting Kinetics, Decay Rates, Pathways, and Isotope Effects

“…Phytate is rather stable against abiotic degradation; however, it can quickly degrade in the presence of phytate-degrading enzymes (Cosgrove and Irving, 1980;Mullaney et al, 2007), which are widespread in the environment (Greiner, 2007;Konietzny and Greiner, 2002;Meek and Nicoletti, 1986;Shan et al, 1993). These enzymes can hydrolyze phytate and generate different inositol phosphate isomers (Greiner and Konietzny, 2011).…”