title: Molecular and biochemical characteristics of β-propeller phytase from marine Pseudomonas sp. BS10-3 and its potential application for animal feed additives.
abstract: Phytate is an antinutritional factor that impacts the bioavailability of essential minerals such as Ca(2+), Mg(2+), Mn(2+), Zn(2+), and Fe(2+) by forming insoluble mineral-phytate salts. These insoluble mineral-phytate salts are hydrolyzed rarely by monogastric animals, because they lack the hydrolyzing phytases and thus excrete the majority of them. The β-propeller phytases (BPPs) hydrolyze these insoluble mineral-phytate salts efficiently. In this study, we cloned a novel BPP gene from a marine Pseudomonas sp. This Pseudomonas BPP gene (PsBPP) had low sequence identity with other known phytases and contained an extra internal repeat domain (residues 24-279) and a typical BPP domain (residues 280-634) at the C-terminus. Structurebased sequence alignment suggested that the N-terminal repeat domain did not possess the active-site residues, whereas the C-terminal BPP domain contained multiple calcium-binding sites, which provide a favorable electrostatic environment for substrate binding and catalytic activity. Thus, we overexpressed the BPP domain from Pseudomonas sp. to potentially hydrolyze insoluble mineral-phytate salts. Purified recombinant PsBPP required Ca(2+) or Fe(2+) for phytase activity, indicating that PsBPP hydrolyzes insoluble Fe(2+)-phytate or Ca2+-phytate salts. The optimal temperature and pH for the hydrolysis of Ca(2+)-phytate by PsBPP were 50°C and 6.0, respectively. Biochemical and kinetic studies clearly showed that PsBPP efficiently hydrolyzed Ca(2+)-phytate salts and yielded myo-inositol 2,4,6-trisphosphate and three phosphate groups as final products. Finally, we showed that PsBPP was highly effective for hydrolyzing rice bran with high phytate content. Taken together, our results suggest that PsBPP has great potential in the animal feed industry for reducing phytates.
authors.affiliation: Lee Gil Ya Cancer and Diabetes Institute, Gachon University Graduate School of Medicine, Incheon 406-840, Republic of Korea.
authors.forename: Seung-Jeung
authors.initials: SJ
authors.lastname: Nam
authors.forename: Young-Ok
authors.initials: YO
authors.lastname: Kim
authors.forename: Tae-Kyung
authors.initials: TK
authors.lastname: Ko
authors.forename: Jin-Ku
authors.initials: JK
authors.lastname: Kang
authors.forename: Kwang-Hoon
authors.initials: KH
authors.lastname: Chun
authors.forename: Joong-Hyuck
authors.initials: JH
authors.lastname: Auh
authors.forename: Chul-Soon
authors.initials: CS
authors.lastname: Lee
authors.forename: In-Kyu
authors.initials: IK
authors.lastname: Lee
authors.forename: Sunghoon
authors.initials: S
authors.lastname: Park
authors.forename: Byung-Chul
authors.initials: BC
authors.lastname: Oh
mesh_terms: D010832:6-Phytase / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D000595:Amino Acid Sequence; D000821:Animal Feed; D059001:Aquatic Organisms; D001483:Base Sequence; D002118:Calcium / Q000378:metabolism; D020134:Catalytic Domain; D003001:Cloning, Molecular; D004795:Enzyme Stability; D005503:Food Additives; D015870:Gene Expression; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007295:Inositol Phosphates / Q000378:metabolism; D007501:Iron / Q000378:metabolism; D007700:Kinetics; D008969:Molecular Sequence Data; D012275:Oryza / Q000378:metabolism; D010833:Phytic Acid / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D011549:Pseudomonas / Q000201:enzymology* / Q000302:isolation & purification; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013696:Temperature
chemical_list: D005503:Food Additives; D007295:Inositol Phosphates; D011994:Recombinant Proteins; C081911:inositol 2,4,6-triphosphate; D010833:Phytic Acid; D007501:Iron; D010832:6-Phytase; D002118:Calcium