Research Center for Infectious Diseases and Immune Dysfunctions

Methylmalonic acidemia is a cause of mental retardation. This disease arise from the functional disturbance of methylmalonyl-CoA mutase. Adenosylcobalamin is the cofactor of mutase. Either adenosylcobalamin deficiency or defect on the mutase itself will result in methylmalonic acidemia. Conventionally, determination of mutase activity was accomplished by radioisotopically measuring methods, using [/sup 14/C]methylmalonyl-CoA as the substrate and measuring the disappearance of [/sup 14/C]methylmalonyl-CoA or amount of [/sup 14/C]succinic acid after hydrolysis of the product succinyl-CoA by perchloric acid; [/sup 14/C]succinic acid was separated from the substrate by paper chromatography, electrophoresis, or potassium permangnate oxidation Those methods were time consuming, laborious, and data about their precision had not been available. We developed a method with HPLC to assay the activity of mutase. It is a rapid and sensitive method. Three fibroblast cell lines obtained from children previously diagnosed as methylmalonic acidemia were reexamined by this newly developed method. Two of them were mutase defect and the other one was adenosylcobalamin deficiency. Although methylmalonic acidemia arising from deficient methylmalonyl-CoA mutase activity is a rare congenital metabolic disorder, it does exist. Etiological designation by MCM assay (AdoCbl deficiency or apoenzyme deficiency) is not only of therapeutic, prognostic values and helpful in genetic counseling, but also necessary in gene study of this enzyme. The present work demonstrated a successful rapid, sensitive and highly reproducible method to determine activity of MCM in crude human placenta extract. This method will be extended to determine MCM activity in cultured human fibroblasts, amniocytes and choriovillus cells with an expect to help clinical confirmation and even prenatal diagnosis.

Project ID:PB8203-1040
External Project ID:DOH82HRC09