An enzymatic method for the determination of butyrobetaine via conversion to carnitine after isolation by high performance liquid chromatography

Abstract An improved procedure for the determination of butyrobetaine [4-( N , N , N -trimethylammonio) butanoate]in plasma and tissue is described. Butyrobetaine was isolated by ion-exchange chromatography and high performance liquid chromatography. The isolation procedure was internally standardized with [ 3 H]butyrobetaine. The recovery of butyrobetaine was > 90%. Following isolation butyrobetaine was enzymatically converted to carnitine using butyrobetaine hydroxylase and the resulting carnitine was assayed using carnitine acetyltransferase and [ 14 C]acetylcoenzyme A. The conversion of butyrobetaine to carnitine and of carnitine to [ 14 C]acetylcarnitine was > 98% as determined by high performance liquid chromatography. Using this method was analysed human sera (healthy controls) and tissues (autopsy) and found the following values: serum, 4.67 nmol/ml; kidney 17.6 nmol/g; liver, 26.5 nmol/g. The serum butyrobetaine values of twins suffering from carnitine deficiency were normal (3.78 and 3.87 nmol/ml), while the carnitine supplementation therapy caused an increase. Animal samples were analyzed and the values were 3–4 times higher than previously reported by others.