Reversal of metabolic block in glycolysis by enzyme replacement in triosephosphate isomerase-deficient cells

Inherited deficiency of the housekeeping enzyme triosephosphate isomerase ( TPI) is the most severe clinical disorder of glycolysis. Homozygotes manife st congenital hemolytic anemia and progressive neuromuscular impairment, wh ich in most cases pursues an inexorable course with fatal outcome in early childhood. No effective therapy is available. Hitherto specific enzyme repl acement has not been attempted in disorders of glycolysis. Primary skeletal muscle myoblasts and Epstein-Barr virus (EBV)-transformed lymphoblastoid c ell lines generated from homozygous TPI-deficient patients were cultured in the presence of exogenous enzyme or cocultured with human K562 erythroleuk emia cells as an exogenous source of TPI. Uptake of active enzyme by TPI-de ficient cells resulted in reversal of intracellular substrate accumulation, with a reduction in dihydroxyacetone phosphate (DHAP) concentration to lev els seen in TPI-competent cells. Evidence of successful metabolic correctio n of TPI deficiency in vitro establishes the feasibility of enzyme replacem ent therapy, and has important implications for the potential role of allog eneic bone marrow transplantation and gene therapy as a means of sustained delivery of functional enzyme in vivo. (C) 1999 by The American Society of Hematology.