Carnitine determination by an enzymatic cycling method with carnitine dehydrogenase.
We describe a highly sensitive and specific method for determining L-carnitine in serum by use of carnitine dehydrogenase (EC 1.1.1.108). The method involves a new enzymatic cycling technique with NADH, thio-NAD+, and carnitine dehydrogenase, and measures the increase of absorbance at 415 nm of thio-NADH produced at 37 degrees C during the reaction: [formula: see text] The calibration curve for L-carnitine in serum was linear between 5 and 250 mumol/L. Analytical recovery was 96.5-106%, and within-run and between-run imprecisions (CV) were 0.66-4.33% and 1.02-2.56%, respectively. This method was free from interference by bilirubin, hemoglobin, various acyl-DL-carnitines, and ascorbate. The procedure is simple, rapid, accurate, and automatable. The amount of free L-carnitine in serum (53.6 +/- 11.7 mumol/L, n = 200) was greater in men than in women (45.1 +/- 14.2 mumol/L, n = 200) (mean +/- SD).
Takahashi
M
M
Asahi Chemical Industry Co., Ltd., Shizuoka-ken, Japan.
Ueda
S
S
Misaki
H
H
Sugiyama
N
N
Matsumoto
K
K
Matsuo
N
N
Murao
S
S
D000421:Alcaligenes / Q000201:enzymology; D000429:Alcohol Oxidoreductases / Q000378:metabolism*; D002331:Carnitine / Q000097:blood*; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008297:Male; D009243:NAD / Q000378:metabolism; D011786:Quality Control; D012016:Reference Values; D012680:Sensitivity and Specificity
D009243:NAD; D000429:Alcohol Oxidoreductases; C019842:carnitine dehydrogenase; D002331:Carnitine