Ca(2+)-inositol phosphate chelation mediates the substrate specificity of beta-propeller phytase.
Inositol phosphates are recognized as having diverse and critical roles in biological systems. In this report, kinetic studies and TLC analysis indicate that beta-propeller phytase is a special class of inositol phosphatase that preferentially recognizes a bidentate (P-Ca(2+)-P) formed between Ca(2+) and two adjacent phosphate groups of its natural substrate phytate (InsP(6)). The specific recognition of a bidentate chelation enables the enzyme to sequentially hydrolyze one of the phosphate groups in a bidentate of Ca(2+)-InsP(6) to yield a myo-inositol trisphosphate (InsP(3)) and three phosphates as the final products. A comparative analysis of (1)H- and (13)C NMR spectroscopy with the aid of 2D NMR confirms that the chemical structure of the final product is myo-Ins(2,4,6)P(3). The catalytic properties of the enzyme suggest a potential model for how the enzyme specifically recognizes its substrate Ca(2+)-InsP(6) and produces myo-Ins(2,4,6)P(3) from Ca(2+)-InsP(6). These findings potentially provide evidence for a selective Ca(2+)-InsPs chelation between Ca(2+) and two adjacent phosphate groups of inositol phosphates.
Oh
Byung-Chul
BC
Department of Biochemistry, School of Medicine, Chungbuk National University, Cheongju 361-763, South Korea. bcoh@chungbuk.ac.kr
Kim
Myung Hee
MH
Yun
Bong-Sik
BS
Choi
Won-Chan
WC
Park
Sung-Chun
SC
Bae
Suk-Chul
SC
Oh
Tae-Kwang
TK
D010832:6-Phytase / Q000737:chemistry* / Q000378:metabolism; D001407:Bacillus / Q000201:enzymology; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D006868:Hydrolysis; D007295:Inositol Phosphates / Q000737:chemistry*; D007700:Kinetics; D010710:Phosphates / Q000737:chemistry; D010833:Phytic Acid / Q000737:chemistry*; D013379:Substrate Specificity
D001426:Bacterial Proteins; D007295:Inositol Phosphates; D010710:Phosphates; C081911:inositol 2,4,6-triphosphate; D010833:Phytic Acid; D010832:6-Phytase