By a News Reporter-Staff News Editor at Life Science Weekly -- Current study results on Sulfur Amino Acids have been published. According to news originating from Louisville, Kentucky, by NewsRx correspondents, research stated, "Methionine synthase (MetH) catalyzes the transfer of a methyl group from methyltetrahydrofolate (CH3-H(4)Folate) to the cob(I)alamin intermediate to form an organometallic Co-C bond, a reaction similar to that of CH3-H(4)Folate:corrinoid/iron-sulfur protein (CFeSP) methyltransferase (MeTr). How precisely it is formed remains elusive because the displacement of a methyl group from the tertiary amine is not a facile reaction."
Our news journalists obtained a quote from the research from the University of Louisville, "To understand the electronic structure and mechanistic details of the MetH-cob(I)-alamin:CH3-H(4)Folate reaction complex, we applied quantum mechanics/molecular mechanics (QM/MM) computations. The hybrid QM/MM calculations reveal the traditionally assumed S(N)2 mechanism for formation the CH3-cob(III)alamin resting state where the activation energy barrier for the S(N)2 reaction was found to be similar to 8-9 kcal/mol, which is comparable with respect to the determined experimental rate constant. However, the possibility of an electron transfer (ET) based radical mechanism consistent with the close-lying diradical states observed from triplet and open-shell singlet states has also been suggested as an alternative, where first an electron transfer from His-on cob(Oalamin to the pterin ring of the protonated CH3-H4Folate takes place, forming the Co-II(d(7))-pterin radical (pi*)1 diradical state, followed by a methyl radical transfer. Although the predicted energy barrier for the ET-mediated radical reaction is comparable to that of the S(N)2 pathway, the major advantage of ET is that a methyl radical can be transferred at a longer distance, which does not require the close proximity of two binding modules of MetH as does the S(N)2 type. In addition, based on the energy barrier of the transition state (TS) in both the protonated (-8-9 kcal/mol) and the unprotonated NS (39 kcal/mol) species of the CH3-H(4)Folate, it can be inferred that the protonation event must takes place either prior to or during the methyl transfer reaction in a ternary complex."
According to the news editors, the research concluded: "The results of the present study including mechanistic insights can have implications to a broad class of corrinoid-methyltransferases, which utilize a CH3-H(4)Folate substrate or its related analogues as methyl donor."
For more information on this research see: Mechanistic Insights for Formation of an Organometallic Co-C Bond in the Methyl Transfer Reaction Catalyzed by Methionine Synthase. Journal of Physical Chemistry B, 2013;117(50):16044-16057. Journal of Physical Chemistry B can be contacted at: Amer Chemical Soc, 1155 16TH St, NW, Washington, DC 20036, USA. (American Chemical Society - www.acs.org; Journal of Physical Chemistry B - www.pubs.acs.org/journal/jpcbfk)
The news correspondents report that additional information may be obtained from N. Kumar, University of Louisville, Dept. of Chem, Louisville, KY 40292, United States (see also Sulfur Amino Acids).
Keywords for this news article include: Kentucky, Synthase, Louisville, Methionine, United States, Nanotechnology, Sulfur Amino Acids, Neutral Amino Acids, Emerging Technologies, Enzymes and Coenzymes, Essential Amino Acids, Organometallic Organosol, North and Central America
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