Adenosine 5-triphosphate reaction with methionine

A4e3 mechanism, 353 Adenine, 431, 1091 Adenosine, 989,1091 Adenosine 3 -5 -cyclic monophosphate (cycUcAMP), 1093 Adenosine diphosphate, 1093 Adenosine 5 -monophosphate, 1092 Adenosine triphosphate, 1093 reaction with methionine, 641 5-Adenosylmethionine, 314, 641 Adipic acid... 

This reaction can be catalyzed by norepinephrine methylpherase. This enzyme is contained in the supernatant fraction of adrenal medulla homogenates. The immediate methyl donor is 18-adenosylmethionine (260, 261). Adenosine triphosphate, Mg, and methionine can replace adenosyl-methionine, but are much less effective in methylation. When the latter compound is employed a stimulation is obtmned with utathione and Mg++... 

The most common example of this process in living organisms is the reaction of the amino acid methionine with adenosine triphosphate (ATP Section 5.8) to give S-adenosylmethionine. The reaction is somewhat unusual in that the biological leaving group in this SN2 process is the triphosphate ion rather than the more frequently seen rliphosphate ion (Section 11.6). 

Adenosine triphosphate, coupled reactions and. 1128-1129 function of, 157, 1127-1128 reaction with glucose, 1129 structure of, 157, 1044 S-Adenosylmethionine, from methionine, 669 function of, 382-383 stereochemistry of, 315 structure of, 1045 Adipic acid, structure of, 753 ADP, sec Adenosine diphosphate Adrenaline, biosynthesis of, 382-383 molecular model of, 323 slructure of, 24... 

Vitamin B12 and folate are involved in the synthesis of methionine from homocysteine in the presence of methionine synthase for which 5-methyl tetrahydrofolate (THF) and methyl-vitamin B12 are cofactors. Methionine in turn along with adenosine triphosphate (ATP) forms 5 -adenosyl methionine (SAM), which is the only methyl group donor in the human central nervous system (CNS). SAM donates methyl groups in number of methylation reactions, involving synthesis of myelin, phospholipids, proteins and neurotransmitters (catecholamine and indoleamines). The methylation cycle is also of importance for the generation of active folate forms. When the methyl group is transferred, SAM is converted to S -adenosyl homocysteine (SAH) which is subsequently converted to homocysteine and adenosine. Hence, homocysteine, vitamin B12 and folate are linked together in one carbon cycle (Moretti et al. 2008). 

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