Methyl transfer reaction

Caste]on H and Wiberg K B 1999 Solvent effects on methyl transfer reactions. 1. The Menshutkin reaction J. Am. Ohem. Soc. 121 2139-46... 

Equation (3.34) without the H X ) and the H 2la terms is identical to the Marcus equation for methyl transfer reactions (Ref. 13). This equation predicts, at the range ( AG0 < a), a linear relationship between AAG0 and AAg by... 

Methyl Transfer Reactions Catalysed by Corrinoid-Containing Enzymes... 

Stupperich E, R Konle (1993) Corrinoid-dependent methyl transfer reactions are involved in methanol and 3,4-dimethoxybenmzoate metabolism by Sporomusa ovata. Appl Environ Microbiol 59 3110-3116. 

With the characterized mechanism, the next key question is the origin of its catalytic power. A prerequisite for this investigation is to reliably compute free energy barriers for both enzyme and solution reactions. By employing on-the-fly Born-Oppenheimer molecular dynamics simulations with the ab initio QM/MM approach and the umbrella sampling method, we have determined free energy profiles for the methyl-transfer reaction catalyzed by the histone lysine methyltransferase SET7/9... 

Co within all compounds of the so-called cobalamin (or B12) family. The biological functions of cobalamin cofactors are defined by their axial substituents either a methyl or an adenosyl group. Both cofactors participate in biosynthesis the former in methyl transfer reactions while the latter is a free radical initiator, abstracting H atoms from substrates. Decades after their initial characterization, the fascination with the biological chemistry of cobalamins remains.1109... 

In mammals and in the majority of bacteria, cobalamin regulates DNA synthesis indirectly through its effect on a step in folate metabolism, catalyzing the synthesis of methionine from homocysteine and 5-methyltetrahydrofolate via two methyl transfer reactions. This cytoplasmic reaction is catalyzed by methionine synthase (5-methyltetrahydrofolate-homocysteine methyl-transferase), which requires methyl cobalamin (MeCbl) (253), one of the two known coenzyme forms of the complex, as its cofactor. 5 -Deoxyadenosyl cobalamin (AdoCbl) (254), the other coenzyme form of cobalamin, occurs within mitochondria. This compound is a cofactor for the enzyme methylmalonyl-CoA mutase, which is responsible for the conversion of T-methylmalonyl CoA to succinyl CoA. This reaction is involved in the metabolism of odd chain fatty acids via propionic acid, as well as amino acids isoleucine, methionine, threonine, and valine. 

In this review we shall not deal with the synthesis of this coordination complex, but we shall deal with the chemical properties of B 12-coenzymes with special emphasis on how these properties relate to Bi2-enzyme mechanisms. Also, we shall show how B -catalyzed methyl-transfer reactions have special significance in the biosynthesis of methylated heavy metals in the aqueous environment, and how the synthesis of these organometallic compounds has special relevance to problems concerned with continuing global environmental health hazards. 

This benzyl-methyl transfer reaction appears to be general in these systems. This process could involve the dehydrogenation of methanol on the surface of palladium, which produces formaldehyde. The formaldehyde could than add to the nitrogen atom to produce a quaternary carbinolamine (Scheme 4.92). 

Interestingly, the methyl-transfer reaction between BMeT and 3-cyano-TV-methylpyridinium (with the highest reduction potential, see Table 7) occurs instantaneously and thus precludes the isolation of the charge-transfer salt. 

Metal complexes, the nucleophilicity of towards organic molecules, 23,1 Methyl transfer reactions, 16,87... 

METHYL TRANSFER REACTIONS USING S-ADENOSYLMETHIONINE MethionineitRNA ligase,... 

In CM terms the proton transfer reaction is very similar to the SN2 reaction of methyl derivatives. The two key configurations which are involved are the reactant and product configurations, [40] and [41]. The arguments that were applicable to methyl transfer reactions now may be utilized for proton transfer reactions. These may be summarized as follows ... 

Bimolecular Decomposition of the Transient Complexes Methyl Transfer Reactions Rearrangement of the Carbon-Skeleton of R (H20)sCrCH02+ as a Hydride Transfer Reducing Agent Alkene Complexes... 

The reaction of [Pt(dien)Cl]Cl with S-adenosyl-L-homocysteine (SAH, a biologically relevant molecule, as it is the coproduct of the methyl transfer reaction by S-adenosyl-L-methionine see Fig. 15) results in a mixture of complexes (193), i.e., the mononuclear complex (1) [Pt(dien)(SAH-S)]2+, with platination of SAH at the sulfur atom, the mononuclear complex (2) [Pt(dien)(SAH-ADJ+, which has a Pt(dien)2+ unit coordinated to the amino group of the homocysteine unit, and the dinuclear complex (3) [ Pt(dien) 2(SAH-S,AD]3+, which has a Pt(dien)2+ unit coordinated to the sulfur atom as well as a Pt(dien)2+... 

Another important group of methyl transfer reactions are those from methyl corrinoids to mercury, tin, arsenic, selenium, and tellurium. For example, Eq. 16-44 describes the methylation of Hg2+. These reactions are of special interest because of the generation of toxic methyl and dimethyl mercury and dimethylarsine. 

The cell walls do not contain muramic acid. Ihe characteristic constituent of the pcplidnglycuns that form lxicten.il cell walls. (2l Their mciaholism differs markedly from bacteria. A number nf coenzymes apparently unique 10 methanogens have been identified. Some of these enzymes are involved in methyl transfer reactions, including the formation of methane. One of the coenzymes is possibly the smallesi coen/yme yet... 

Vitamin B]2 is a red crystalline, cobalt-containing compound that can be isolated from the liver. It has a functional role in preventing pernicious anaemia and also serves as a coenzyme in hydrogen and methyl transfer reactions (Co appears to be the only metal in vivo catalyzing C transfer reactions O and N transfers are more common). Vitamin B12 is also a growth-promoting factor for several microorganisms. 

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