### Abstract

Ab initio quantum mechanical calculations were used to study the hydrolysis H_{4}P_{2}O_{7} + H_{2}O2H_{3}PO_{4}, as well as some molecular properties of the reactants and products. SCF calculations with several basis sets ranging from minimal to extended with polarization functions were used to look at the basis dependency of the reaction enthalpies and optimized geometries. Although the minimal basis sets yield erratic predictions of the enthalpy, when a more extended basis (3-21G^{*}) was used for the geometry optimization, and the total energies of the reactants and products were computed with this and larger basis sets, we obtained more consistent predictions of the structural properties of the POP bridge and of the heat of the hydrolysis reaction (ΔE = -7.39 kcal/mol at the SCF/6-31G^{**} level). A comparison is made with previous estimates performed with smaller basis sets and without taking into account the electron correlation effects, which are calculated in the present work. The inclusion of the zero point energy calculated using the harmonic approximation, and of the electronic correlation energy determined at the MBPT(2) level, raised the computed heat of the reaction to -3.83 kcal/mol, and when an estimate for the thermal energy was added, the value obtained was of -3.38 kcal/mol. In conclusion, we found that the hydrolysis of pyrophosphate should be exothermic in the gas phase. The implications of this result in relation to some recent theories about enzyme catalysis are discussed.

Original language | English (US) |
---|---|

Pages (from-to) | 205-214 |

Number of pages | 10 |

Journal | Biochimica et Biophysica Acta (BBA)/Protein Structure and Molecular |

Volume | 1080 |

Issue number | 3 |

DOIs | |

State | Published - Nov 15 1991 |

### Fingerprint

### Keywords

- Ab initio calculation
- Enzyme mechanism
- Gas-phase reaction
- Pyrophosphate hydrolysis

### ASJC Scopus subject areas

- Biochemistry
- Biophysics
- Molecular Biology
- Structural Biology

### Cite this

*Biochimica et Biophysica Acta (BBA)/Protein Structure and Molecular*,

*1080*(3), 205-214. https://doi.org/10.1016/0167-4838(91)90003-I

**Ab initio calculations of the pyrophosphate hydrolysis reaction.** / Saint-Martin, Humberto; Blake, Iván Ortega; Leś, Andrzej; Adamowicz, Ludwik.

Research output: Contribution to journal › Article

*Biochimica et Biophysica Acta (BBA)/Protein Structure and Molecular*, vol. 1080, no. 3, pp. 205-214. https://doi.org/10.1016/0167-4838(91)90003-I

}

TY - JOUR

T1 - Ab initio calculations of the pyrophosphate hydrolysis reaction

AU - Saint-Martin, Humberto

AU - Blake, Iván Ortega

AU - Leś, Andrzej

AU - Adamowicz, Ludwik

PY - 1991/11/15

Y1 - 1991/11/15

N2 - Ab initio quantum mechanical calculations were used to study the hydrolysis H4P2O7 + H2O2H3PO4, as well as some molecular properties of the reactants and products. SCF calculations with several basis sets ranging from minimal to extended with polarization functions were used to look at the basis dependency of the reaction enthalpies and optimized geometries. Although the minimal basis sets yield erratic predictions of the enthalpy, when a more extended basis (3-21G*) was used for the geometry optimization, and the total energies of the reactants and products were computed with this and larger basis sets, we obtained more consistent predictions of the structural properties of the POP bridge and of the heat of the hydrolysis reaction (ΔE = -7.39 kcal/mol at the SCF/6-31G** level). A comparison is made with previous estimates performed with smaller basis sets and without taking into account the electron correlation effects, which are calculated in the present work. The inclusion of the zero point energy calculated using the harmonic approximation, and of the electronic correlation energy determined at the MBPT(2) level, raised the computed heat of the reaction to -3.83 kcal/mol, and when an estimate for the thermal energy was added, the value obtained was of -3.38 kcal/mol. In conclusion, we found that the hydrolysis of pyrophosphate should be exothermic in the gas phase. The implications of this result in relation to some recent theories about enzyme catalysis are discussed.

AB - Ab initio quantum mechanical calculations were used to study the hydrolysis H4P2O7 + H2O2H3PO4, as well as some molecular properties of the reactants and products. SCF calculations with several basis sets ranging from minimal to extended with polarization functions were used to look at the basis dependency of the reaction enthalpies and optimized geometries. Although the minimal basis sets yield erratic predictions of the enthalpy, when a more extended basis (3-21G*) was used for the geometry optimization, and the total energies of the reactants and products were computed with this and larger basis sets, we obtained more consistent predictions of the structural properties of the POP bridge and of the heat of the hydrolysis reaction (ΔE = -7.39 kcal/mol at the SCF/6-31G** level). A comparison is made with previous estimates performed with smaller basis sets and without taking into account the electron correlation effects, which are calculated in the present work. The inclusion of the zero point energy calculated using the harmonic approximation, and of the electronic correlation energy determined at the MBPT(2) level, raised the computed heat of the reaction to -3.83 kcal/mol, and when an estimate for the thermal energy was added, the value obtained was of -3.38 kcal/mol. In conclusion, we found that the hydrolysis of pyrophosphate should be exothermic in the gas phase. The implications of this result in relation to some recent theories about enzyme catalysis are discussed.

KW - Ab initio calculation

KW - Enzyme mechanism

KW - Gas-phase reaction

KW - Pyrophosphate hydrolysis

UR - http://www.scopus.com/inward/record.url?scp=0025938438&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0025938438&partnerID=8YFLogxK

U2 - 10.1016/0167-4838(91)90003-I

DO - 10.1016/0167-4838(91)90003-I

M3 - Article

C2 - 1659451

AN - SCOPUS:0025938438

VL - 1080

SP - 205

EP - 214

JO - Biochimica et Biophysica Acta - Proteins and Proteomics

JF - Biochimica et Biophysica Acta - Proteins and Proteomics

SN - 1570-9639

IS - 3

ER -