Glycolytic defects in muscle: aspects of collaboration between basic science and clinical medicine.
The molecular heterogeneities of enzyme abnormality have been identified successfully since 1990 for major clinical entities of glycogenolytic and glycolytic defects in skeletal muscle. The interchange between clinical medicine and basic science, which enabled these achievements, has a long history. This review introduces several important examples of this interchange, which has borne much fruit in the comprehensive understanding of glycogenolysis-glycolysis in skeletal muscle and the related defects that cause various metabolic diseases. For instance, the presence of "glycogen synthase" was mainly suggested by the pathophysiology of McArdle's disease. Clinical manifestations of muscle phosphofructokinase (PFK) deficiency have indicated that there could be PFK isozymes under separate genetic control. Although glycolysis is a unidirectional pathway, enzyme defects at each step do not necessarily cause similar manifestations. Glycogen accumulation is mostly associated with enzyme defects in glycogenolysis and in the first stage of glycolysis. Since the original report of phosphoglycerate mutase deficiency in 1981, no newly recognized glycolytic defects have been presented. Glycolytic steps for which no enzyme deficiency has been identified seem to provide another important impetus for further study of "fail-safe" mechanisms in regard to monogenic disorders.