Diol Dehydratase-Reactivase Is Essential for Recycling of Coenzyme B12in Diol Dehydratase

Biochemistry ◽  
2015 ◽  
Vol 55 (1) ◽  
pp. 69-78 ◽  
Author(s):  
Tetsuo Toraya ◽  
Aya Tanokuchi ◽  
Ai Yamasaki ◽  
Takehiro Nakamura ◽  
Kenichi Ogura ◽  
...  
Keyword(s):  
Diol Dehydratase

Directionality and the Role of Polarization in Electric Field Effects on Radical Stability

2017 ◽  
Vol 70 (4) ◽  
pp. 367 ◽  
Author(s):  
Ganna Gryn'ova ◽  
Michelle L. Coote
Keyword(s):  
Electric Field ◽  
External Electric Field ◽  
Radical Reactions ◽  
Electric Field Effects ◽  
Dissociation Energies ◽  
Barrier Heights ◽  
Diol Dehydratase ◽  
Group A ◽  
Activity Of Enzymes ◽  
The Stability

Accurate quantum-chemical calculations are used to analyze the effects of charges on the kinetics and thermodynamics of radical reactions, with specific attention given to the origin and directionality of the effects. Conventionally, large effects of the charges are expected to occur in systems with pronounced charge-separated resonance contributors. The nature (stabilization or destabilization) and magnitude of these effects thus depend on the orientation of the interacting multipoles. However, we show that a significant component of the stabilizing effects of the external electric field is largely independent of the orientation of external electric field (e.g. a charged functional group, a point charge, or an electrode) and occurs even in the absence of any pre-existing charge separation. This effect arises from polarization of the electron density of the molecule induced by the electric field. This polarization effect is greater for highly delocalized species such as resonance-stabilized radicals and transition states of radical reactions. We show that this effect on the stability of such species is preserved in chemical reaction energies, leading to lower bond-dissociation energies and barrier heights. Finally, our simplified modelling of the diol dehydratase-catalyzed 1,2-hydroxyl shift indicates that such stabilizing polarization is likely to contribute to the catalytic activity of enzymes.

Concerning the intermediacy of organic radicals in vitamin B 12 -dependent enzymic reactions

1985 ◽  
Vol 311 (1152) ◽  
pp. 531-544 ◽  
Keyword(s):  
Carbon Atom ◽  
Crystal Structures ◽  
Organic Radicals ◽  
Vitamin B ◽  
Molecular Rearrangements ◽  
Alkyl Radicals ◽  
Model Studies ◽  
Diol Dehydratase ◽  
Vitamin B 12

The vitamin B 12 coenzyme adenosylcobalamin assists the enzymic catalysis of molecular rearrangements of the type in which the migrating group X can be OH, NH 2 or a suitable substituted carbon atom such as C (=CH 2 )CO 2 H. This paper discusses evidence for the participation of organic radicals as intermediates in these reactions. Theoretical and model studies supporting the intermediacy of radicals in the reactions catalysed by the enzymes diol dehydratase and α-methyleneglutarate mutase are described. For the model studies, alkyl radicals, alkylcobaloximes (alkyl represents, for example, ethoxycarbonyl substituted, but-3-enyl and cyclopropylmethyl) and also dihydroxyalkylcobalamins have been investigated. The Co-C α -C β angle of 125° in adenosylcobalamin is shown to be an ‘especial’ angle by analysis of the crystal structures of R - and S -2,3-dihydroxypropylcobalamin.

Crystallization and preliminary X-ray study of two crystal forms of Klebsiella oxytoca diol dehydratase–cyanocobalamin complex

1999 ◽  
Vol 55 (4) ◽  
pp. 907-909 ◽  
Author(s):  
Jun Masuda ◽  
Tetsuya Yamaguchi ◽  
Takamasa Tobimatsu ◽  
Tetsuo Toraya ◽  
Kyoko Suto ◽  
...  
Keyword(s):  
Klebsiella Oxytoca ◽  
Crystal Form ◽  
Unit Cell ◽  
Unit Cell Parameters ◽  
Crystal Forms ◽  
Space Group ◽  
X Ray ◽  
Cell Parameters ◽  
Diol Dehydratase ◽  
Replacement Method

Two crystal forms of Klebsiella oxytoca diol dehydratase complexed with cyanocobalamin have been obtained and preliminary crystallographic experiments have been performed. The crystals belong to two different space groups, depending on the crystallization conditions. One crystal (form I) belongs to space group P212121 with unit-cell parameters a = 76.2, b = 122.3, c = 209.6 Å, and diffracts to 2.2 Å resolution using an X-ray beam from a synchrotron radiation source. The other crystal (form II) belongs to space group P21 with unit-cell parameters a = 75.4, b = 132.7, c = 298.8 Å, β = 91.9°, and diffracts to 3.0 Å resolution. For the purpose of structure determination, a heavy-atom derivative search was carried out and some mercuric derivatives were found to be promising. Structure analysis by the multiple isomorphous replacement method is now under way.

Mechanism-based Inactivation of Coenzyme B12-dependent Diol Dehydratase by 3-Unsaturated 1,2-Diols and Thioglycerol

2008 ◽  
Vol 144 (4) ◽  
pp. 437-446 ◽  
Author(s):  
T. Toraya ◽  
N. Tamura ◽  
T. Watanabe ◽  
M. Yamanishi ◽  
N. Hieda ◽  
...  
Keyword(s):  
Coenzyme B12 ◽  
Diol Dehydratase

scholarly journals Structural Rationalization for the Lack of Stereospecificity in Coenzyme B12-dependent Diol Dehydratase

2003 ◽  
Vol 278 (25) ◽  
pp. 22717-22725 ◽  
Author(s):  
Naoki Shibata ◽  
Yuka Nakanishi ◽  
Masaki Fukuoka ◽  
Mamoru Yamanishi ◽  
Noritake Yasuoka ◽  
...  
Keyword(s):  
Coenzyme B12 ◽  
Diol Dehydratase
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