Fluorometric Assay of Rat Tissue N-Methyltransferases with Nicotinamide and Four Isomeric Methylnicotinamides

概要

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Nicotinamide (NA) and its four isomeric methyl analogs [2-, 4-, 5- and 6-methylnicotinamides (MNs)] were tested as substrates for nicotinamide N-methyltransferase (NNMT) and amine N-methyltransferase (ANMT) using rat liver, kidney, spleen and brain 9000×g supernatant fluids as model enzyme preparations. The N-methylated products were determined fluorometrically by their reaction with acetophenone or 4-methoxybenzaldehyde to form fluorescent 2,7-naphthyridine derivatives, and the lower limits of the determination were 8-30 pmol/100μl. N-Methyltransferase activities were detected in the liver with NA, 4-MN and 5-MN, and in the brain and spleen with 4-MN. On this basis, 5-MN is considered to be a selective substrate for NNMT in addition to NA, which is a known methyl acceptor for this enzyme. Although 4-MN appears to serve as a methyl acceptor for both ANMT and NNMT, it seems to be essentially a selective substrate for brain ANMT because of the absence of NNMT in brain. The fluorometric methods used here are also very useful because of their simplicity, sensitivity and selectivity.
社団法人日本薬学会の論文
1992-01-25