HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY OF COENZYME-A ESTERS FORMED BY TRANSESTERIFICATION OF SHORT-CHAIN ACYLCARNITINES - DIAGNOSIS OF ACIDEMIAS BY URINARY ANALYSIS

A protocol for the identification and estimation of short-chain esters of carnitine is described; it is useful for the diagnosis of acidemias. By this method, carnitine esters in urine are converted to coenzyme A esters enzymatically with carnitine acetyltransferase (CAT): .**GRAPHIC**. The coenzyme A esters are separated by high-performance liquid chromatography using a radical compression system with a C8 Radial-Pak cartridge and a mobile phase containing 0.025 M tetraethylammonium phosphate in a linear gradient of 1 to 50% methanol. Coenzyme A esters are quantitated by integrator determination of the area under the 254-nm absorption peaks. Enzymatic conversion approaches 100% for acetyl and propionyl esters except in the presence of high levels of free carnitine, which lowers the proportion of ester as acyl-CoA at equilibrium. However, since acidemia patients produce urine low in free carnitine, this problem is minimized. The method is rapid and simple and identifies propionic, methylmalonic, and isovaleric acidemias.