[Donors and receptors of biologically labile methyl groups: characterization with a nicotinamide-trigonelline system].

The problem of transmethylations, the genesis of the labile methyl groups, the chemical structure of a transmethylating active substance are briefly explained and discussed. A methodology to characterize quickly the substances donor and acceptor of methyl groups is here described: it utilizes the ox crystalline lens in the presence of nicotinamide. The methodology is based on the irreversible system nicotinamide-trigonellinamide, by means of the vitamin B1 as catalyst.