Detection of Krabbe disease using tritiated galactosylceramides with medium-chain fatty acids

Galactocerebrosidase (galactosylceramidase) assays using tritiated galactosylceramides with saturated, medium-chain fatty acids (C6-C11) were found to be more sensitive and more reliable than the commonly used assays with long-chain and very long-chain substrates (C16-C26). Galactosylsphingosine (psychosine) was tritiated by a modification of the galactose oxidase-sodium borohydride method, and 19 galactosylceramides were synthesized by the direct coupling of galactosylsphingosine with fatty acids of varying lengths (C6 to C24). The highest specific activities of normal prenatal and postnatal enzyme preparations were obtained with the C6 and C8 derivatives, which were six and five times more sensitive, respectively, than the C16 substrate. The residual activities in enzyme preparations from fetuses and children with Krabbe disease were proportionally increased. Our experience indicates that these substrates can provide a sensitive and reliable means for the prenatal and postnatal detection of Krabbe disease.