Neuraminidase activity in the mucolipidoses (types I, II and III) and the cherry-red spot myoclonus syndrome

Abstract

Two neuraminidase (EC 3.2.1.18) components, A and B, were distinguished in cultured skin fibroblasts on the basis of thermolability at 37°C. The more labile component (A) t 1 2 = 4.7–5.3 min at 37°C, comprises 66–90% of total neuraminidase activity when determined using sodium ( 4- methylumbelliferyl-α- d-N- acetylneuraminate ) (MU- α- N) as substrate. Activity was assayed at 0°C for 18 h instead of 37°C to fully determine both thermolabile and thermostable components. Diminished activity was noted in cultured fibroblasts from mucolipidoses I, II and III (MLI, MLII, MLIII) and the cherry-red spot myoclonus syndrome (CRSM) patients when assayed at both 0 and 37°C with either MU- α- N or each of a series of α(2 → 3)- and α(2 → 6)-linked N-acetylneuraminyl-oligosaccharides. Increased sensitivity and rapidity of analyses were achieved using MU- α- N as substrate in determining neuraminidase activity. Results from two obligate heterozygote MLI cell lines (14.5 and 8.0% of control activity) indicate that the MU- α- N substrate could be useful for heterozygote detection.