Methionine 5-adenosyl-, selective methylations with

The biological role of PIMT involves the selective methylation of isoaspartate residues followed by a demethylation step to reform the succi-nimide intermediate. The demethylation causes the release of methanol which can be converted to formaldehyde and finally to formic acid, as demonstrated in rat brain preparations. It was found that S-adenosyl-methionine (SAM), the methyl donor, caused formaldehyde levels to rise in the rat brain homogenates, thus suggesting that excessive formaldehyde may be a precipitating factor in Parkinsons s disease (PD) (Lee et ah, 2008). It is possible that carnosine could suppress formaldehyde toxicity by reacting with it to generate a carnosine-formaldehyde adduct. This should be a relatively easy experiment to perform to test this prediction. 

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