In vitro analysis of hepatic carnitine biosynthesis in human systemic carnitine deficiency

The syndrome of systemic carnitine deficiency (progressive muscle weakness, recurrent metabolic encephalopathy, low liver and muscle and fluctuating serum carnitine levels) has been attributed to a defect of carnitine biosynthesis. We determined activities in liver of the four enzymes which convert ϵ-N-trimethyl-l-lysine to l-carnitine in three patients with systemic carnitine deficiency and in 12 control subjects. In the three patients all enzyme activities were within the normal range except one, which was slightly below the normal range. We conclude that in systemic carnitine deficiency no enzymatic defect exists in the conversion of ϵ-N-trimethyl-l-lysine to carnitine.