Enzyme activities and phospholipid storage patterns in brain and spleen samples from niemann‐pick disease variants: a comparison of neuropathic and non‐neuropathic forms

Phospholipid levels and enzyme activities were measured in brain and spleen samples from patients with the three major variants of Niemann‐Pick disease. Accumulations of sphingomyelin and bis(monoacylglycero)phosphate were demonstrated in spleen from types A and B and group C Niemann‐Pick disease, whereas only in type A Niemann‐Pick brain was the sphingomyelin concentration increased. Sphingomyelinase activity was markedly deficient in type A Niemann‐Pick brain and spleen but residual activity of approximately 12% of control was measured in type B Niemann‐Pick brain. Normal or raised sphingomyelinase and β‐glucosidase activities were measured in group C Niemann‐Pick brain and spleen. Significant (17% of control) residual β‐glucosidase activity was also measured in non‐neuropathic Gaucher brain. Normal levels of neutral sphingomyelinase activity were measured in brain samples from the three variants of Niemann‐Pick disease. Acid sphingomyelinase activity in group C Niemann‐Pick brain appeared normal with respect to enzyme extraction, pH optimum (pH5.0) and apparent K m (approximately 0.4 mmol/L). Isoelectric focusing of brain sphingomyelinase revealed a degree of heterogeneity with activity peaks between pI 4.5 and 6.5. No defect was observed in group C Niemann‐Pick brain and, although attenuated, all peaks were present in type B Niemann‐Pick brain.