Fluorometric assay of rat brain N-methyltransferase with 4-methylnicotinamide.
A fluorometric method for the assay of rat brain N-methyltransferase (NMT) has been developed using rat brain 9000 x g supernatant fluid as an enzyme preparation. The method is based on the enzyme reaction at pH 8.6 using 4-methylnicotinamide (4-MN) as the methyl acceptor substrate in the presence of cofactor S-adenosyl-L-methionine (AdoMet), and the fluorometric determination of the product 1,4-dimethylnicotinamide by means of its reaction with 4-methoxybenzaldehyde. The apparent Km values for 4-MN and AdoMet were 0.47 mM and 19 microM, respectively. The method was successfully applied to the studies of age- and sex-related differences of brain NMT activity in rats. The enzyme activity decreased gradually between 3 and 14 weeks of age whereas there were no differences between males and females in the levels of NMT activity.
Sano
A
A
Faculty of Pharmaceutical Sciences, Science University of Tokyo, Japan.
Endo
N
N
Takitani
S
S
D000375:Aging / Q000378:metabolism; D000818:Animals; D001921:Brain / Q000201:enzymology*; D002851:Chromatography, High Pressure Liquid; D004795:Enzyme Stability; D005260:Female; D007700:Kinetics; D008297:Male; D008780:Methyltransferases / Q000032:analysis*; D009536:Niacinamide / Q000031:analogs & derivatives* / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012436:S-Adenosylmethionine / Q000378:metabolism; D013050:Spectrometry, Fluorescence
C082979:1,4-dimethylnicotinamide; D009536:Niacinamide; C063648:4-methylnicotinamide; D012436:S-Adenosylmethionine; D008780:Methyltransferases